A Work in Progress
If you're like me, you started improvising because you love it. I'm sure some people dip in and out. Maybe they take a 101 class to feel more comfortable speaking in front of people. Perhaps they go to 201 because they're the funniest person in their friend group. I'll be vulnerable for a moment and say that I'm doing this because I want to be the best at this. Not that I could tell you what that means.
My inner monologue in every class and team I'm in.
Wanting to be the best at something is fine. It's even helpful. Being driven and having ambition can make you better. It can be motivating. It's good. It can also be scary when it becomes jealousy, bitterness, and vindictiveness. I'd be lying if I said I'd never dealt with those emotions. I'm trying to get better just like everyone else. There's a gap between what I am and what I want to be.
This gap is the Dunning-Kruger effect.

“Nobody tells this to people who are beginners, I wish someone told me. All of us who do creative work, we get into it because we have good taste. But there is this gap. For the first couple years you make stuff, it’s just not that good. It’s trying to be good, it has potential, but it’s not. But your taste, the thing that got you into the game, is still killer. And your taste is why your work disappoints you. A lot of people never get past this phase, they quit. Most people I know who do interesting, creative work went through years of this. We know our work doesn’t have this special thing that we want it to have. We all go through this. And if you are just starting out or you are still in this phase, you gotta know its normal and the most important thing you can do is do a lot of work. Put yourself on a deadline so that every week you will finish one story. It is only by going through a volume of work that you will close that gap, and your work will be as good as your ambitions. And I took longer to figure out how to do this than anyone I’ve ever met. It’s gonna take awhile. It’s normal to take awhile. You’ve just gotta fight your way through.”
—Ira Glass
If you can see the gap between where you are and where you want to be, you have good taste. You seem to know what's relevant, natural, and funny, and how funny you want to be. This is a good thing. It means you have a target. Unfortunately, you currently lack the necessary skills to achieve your target. Instead of thinking about how much you suck, think about how good it is that you know what you need to do to get better. Everything about Improv is a skill; skills are things you can get better at by working on them.