Your voice won't ever change if you're not using it.
In my first video I had a lot of confidence issues, talking was a pain in the a**, was not fond of it, but through recording over and over and over again you're able to get into the groove, and it's something you have to do. Build up confidence, train your voice, expand your vocal cords, treat the recording as if its the easiest thing in the world, etc.
Can you become big without commentary, sure, but how many actually do? Maybe if you're an amazing gamer that goes through pro circuits you could succeed getting some fans, but otherwise it will be amazingly hard. GTA is a great game, but without commentary there's really nothing to see.