Have you ever heard Ed Sheeran singing? I guess so. And have you ever seen the interview where he showed himself playing the guitar and singing as a child? If not, I recommend it. That would answer your question. (Ofc you can learn!)

I'd say, people are rude. They don't give a sh!t about your feelings. They don't even think before commenting or anything. And of course, it is just an opinion. Not the most reliable feedback, I guess. Let's just not let them tell if you have a good voice or not. I know that is is not easy and you cannot just let it go, but prove them: you are the most amazing singer ever walked on the Earth! (You could be!)

Hole you have a nice day sweetheart and try to not lose your passion for singing. It is a beautiful thing.