It's definitely not a bad idea to stream when you're shy and have low self-esteem. In fact, it's a great idea!
Last year, I actually started streaming to help improve my social anxiety. My self-esteem was very low and I thought that streaming would help me become more confident. Starting out, I was really quiet and barely made any commentary. The words I said had no life in them, and they were mostly mumbled and stuttered. Just like you, I thought I wasn't going to be very entertaining (to be honest, I still feel the same way a bit) and bore people away from my stream. But that wasn't the case. People started coming in and stayed. Most of them talked in chat and I replied to them with the very little conversation skills that I had. As soon as I realized that people were watching me, that pushed me to make more commentary.
Time passed and I simply got used to streaming. I became more active on the mic and made it a habit to talk to my viewers. I then noticed that I was a lot different from when I first started out. If you want, you can check out my old highlights as examples. They're not that great, but you might be able to notice the change in my speaking. This was maybe the second day I started streaming. I was really quiet and mumbled badly. This one was two weeks later from the previous highlight. I had a better mic and played a different game in this one, but I don't think that made much of a difference. I started talking more with my viewers, and the duration of my silences were shorter. I still stutter and you can tell that a lot of words came out unnaturally. Now here's me another two week later, or a month after I started streaming. Again, in this one it's quite a different situation as the ones I was in in the previous highlights. I'm basically playing with other people and in a competitive mood, but they aren't big enough factors to measure the change in my streaming performance. You can see that my voice is much stronger. There's no hesitance in my words and I fire them away naturally. I'm much more expressive with my emotions. I was more lively. It's amazing how much I changed in a month.
To put it shortly, you might struggle at first. If you keep streaming and get used to it, you will become a natural at it. Once you realize that people are there to watch you, you will become more motivated. And you will definitely have people to watch you. If you're not a very likeable person like myself, you will still build up an audience that actually likes you for who you are. At the very least, you can make people stay with the gameplay and interaction. Viewers love it when the streamer always talks to them.
Sure it depends on each individual. Maybe it was easier for me because my level of issues wasn't that high. Or maybe it's situational where my viewer count increased out of pure luck, and my confidence grew out of that luck. Who knows. But I can't easily deny my growth like that.
It's kind of discouraging to say this after writing such a positive essay, but at the start of this year, I fell back into my horrible depression (for various reasons not related to streaming) and became busy. Unfortunately, I gave up on my streaming schedule and barely streamed. However, I do plan on getting back to streaming soon once I get things settled. Depression is different from shyness/low self-esteem. I can definitely say that I am less shy than before and still talk considerably better than before I started streaming. I hope this post helps you make a decision. Good luck! (grr I unnecessarily typed too much I'm sorry)