Well, let me first start off by saying that writing bots, like writing anything creatively, is going to be something that's personal to you, and as such, everybody is going to approach it differently and get different results, we are after all unique, each one of us.
But setting that aside, there are a few ways to improve the way you write bots and the things I'll talk about in this guide, how to make them more creative.

Is creativity nessecsary to make good bots?

This is a complex question and will depend on what you are trying to achieve. If you just want to make a bot that gets lots of downloads, then the answer is a very simple no. Taking a quick look at the most downloaded bots on the Chub page, you'll see several bots with simple premises and token counts in the low hundreds with incredible download numbers. So no, being creative isn't required if you just want to get a lot of downloads.

However, making a bot that goes beyond "Female family member with X-quirk" is something that will be far more important for your bot to become beloved. Compare, for example, a bot like c.ⱯI and Kayla. Despite having almost twice as many downloads, I have not seen a single log of Kayla to this day, while logs for little njegger get posted almost daily.
Now, there is nothing wrong with not creating a groundbreaking OC each time you make a bot, because that's simply not going to happen. However, what you should try to do is imbue all bots you create with at least one twist to make them stand out, whether that be in their personality or the scenario you are going for.

It's also worth mentioning that writing unique and creative bots simply feel better than making more generic coombots, and that's what's most important. I have made as many bots as I have because I enjoy the different scenarios and ways they interact with me. If I was writing "Your sister but she's horny" I wouldn't have made it past 20 bots.

Types of creativity

In general there are two ways to make a bot creative, the scenario and their personality.

Scenario creative

The first one is far more simple: simply write a bot and put it in at least a semi-complex scenario. Let's take my bot Ellenox as an example. Purely speaking, she is not very complex. She's a shy and meek goblin with a petite build, however unlike some goblin-bots that start out with "You find a goblin in a back-alley, she turns to you with a broad grin on her face, seemingly in heat." Ellenox's whole thing is her disney princess-like ideas of chivalry and knights in shining armor being contrasted against the cruel reality of human nobility. (with the exception of you of course)
This kind of creativity makes writing bots quite easy, since once you've got a fun and unique scenario, all you need to do is create a bot around that.
I have made several "coombots" (Camilla, Okami, Rujika and Olivia to name a few.) but by making a unique scenario for each bot I (and seemingly others) enjoy them far more.

Another advantage of a creative scenario is it allows you to direct the stories people will write. While cooming is well and good, I believe the most powerful moments with chatbots are when you both experience the storybeats that would come in any good novel, and a scenario is a good way to nudge people in the direction of a story. If we're going back to Ellenox, the story I push people into writing is a classic misunderstood princess and a noble hero to save her, a bit clique yes, but it makes people engage with the bot in a totally different way than just trying to coom with them.

Some examples of bots with good scenarios are: Gretchen, Snatch ratchit, public-highschool-survival, Anlotte, Fuka and pretty much anything from anonaugus or nuggest.

Ok but how do I come up with scenarios?

This is the tricky part and I will be the first to admit that I most likely have an easier time than most with this. As a creative person in general I can look at an image and come up with a story in less than a second, but even if you are the most uncreative person alive you will also be able to write good scenarios.

Now I use pre-existing images for my bots, which means that my creative process normally starts when I find an image I like and come up with a scenario based on it, but if you use your own images or want to come up with a scenario from scratch there are a few ways to do so.
Firstly, you can base a bot on a scenario you have run with another bot. My Annik/Kurtis card, for example, was based on a scenario I did with a far more bare-bones slave trainer bot on CAI back when. So if you find a particular scenario really good with a certain bot, don't be afraid to extract it and polish it even further as your own bot. Be mindful of what made the scenario enjoyable in the first place, and write your bot to take advantage of that.
Secondly, you could simply think about a type of scenario you think is missing from Chub. Maybe it's a failed lab experiment having imprinted on you or a political marriage between differing fantasy races, either way, identify a niche that hasn't been filled and make a bot based on it.

Music can be great for coming up with characters and scenarios, so if you are struggling, put on a random playlist and simply let your mind wander. Also, there is nothing wrong with taking inspiration from a famous hentai or similar, as long as you do the source material justice. I have a few popular bots like Umeko and Aizome that are straight-up the characters from their respective hentai comics.

Personality creative

The second way to make a bot more creative is not to have a unique scenario but instead to write them to behave in a distinct way.

I'll be honest, I do not have as much experience with this type of bot, but I'll try to explain it anyway.
Chatbots tend to write in a very clean and elegant way, which is good for most situations but can get a bit samey after a while, and as such, a bot that manages to stand out by the way they speak and behaves will set itself apart from others. This can be altering a bot's speech patterns from quite minor changes (Nascha) to major ones (c.ⱯI), but how a bot behaves can also set it apart. (Fucina is a great example of this)
This can be quite tricky as different AI-models will handle speech differently, and more creative and unique speech-patterns will handle differently on various models. In general, the stronger a model is, the better it will be at handling unique speech-form.
(Attached is a image illustrating a bot that's supposed be a fiery black woman who speaks in a "black" southern accent on three models.)

Making a bot's personality unique and creative will take quite alot of tinkering to get it just right, however when a truly unique bot comes along people will notice it.

I do not have as many concrete tips to help you with this part as I did with the last one since, as I said, I find my creativity comes more from scenarios. However, don't be afraid to experiment with for example speech styles. Maybe your bots have a very unique, one-piece-esque laugh, or maybe they're just a lovable idiot like the Negotiatrix? Experiment and find what you like, because these types of bots almost always come from the heart, and trying to force one out isn't going to work. For this type of bot, example messages are your best friend, as they allow you to replace the clean AI personality with something more unique.

General tips

This is going to be obvious, but writing from experience is going to give you a big boost when it comes to how creative and believable your bot will be. People will always be able to write about what they have experienced firsthand more convincingly than something they haven't experienced.

Generally, plaintext is going to produce the most creative bots. Something like W++ which is mostly just about easily defining body type and personality, makes it difficult to write the smaller nuances that a lot of great bots have. I'm not saying you can't make a creative bot with W++, but it's generally harder.

Only make bots that you can see yourself enjoying. It should be obvious, but never make something that you don't find appealing, it's not going to come out well. Being bisexual does kind of help with this since you can take advantage of ideas for both male and female bots that pop into your head.

Don't be afraid to post your stuff and have people critique it. We all start off somewhere, and while you can certainly make good bots only you play with, having others check out your work and give you feedback on it will always be valuable. Yes, you might get some negative reviews or comments, but literally everybody does in some form or another, and absolutely nothing will come of it. Take the good with the bad and pick out anything useful from it to improve your next work.

Have fun. I know it's clique, but if you don't enjoy the process of making a bot, it doesn't matter how sweet that hit of (You)'s are or even the rush of getting a long, you'll burn yourself out and end up hating making bots, something that will certainly not lead to good results.