Who cares if it already exists, just make it.
Also consider the possibility when the other, more popular projects got enshittified. Now the fleeing users have an option to switch to your project. It actually happened on one of my side project. I made it because I want to try building my own version of X. It got ~2000 users, but later down the road, X got sold to a new shitty owner that waste no time to enshittify it, and my side project suddenly grow to 20,000 users overnight.
It's not 3rd party app developers fault that kbin didn't have any stable api yet. Now that they fast track the api development, I think we can expect more 3rd party apps coming soon.