People don't know you well enough on the internet to give you specific advice, so they have to tell you something vague. They think you know exactly how you can improve yourself, but if you don't know what to do, this isn't helpful at all.
Besides that, what could you do instead? You can't change women, you can only change yourself. You also could give up entirely on romantic relationships and do something else instead.
If you are really ugly and undesirable, then there should also be ugly and undesirable women too. Either they are extremely rare, or you don't want them because they are ugly and undesirable.
That you can't really change your looks is true, and it's something you can only change a bit. But it doesn't mean, that there are only beautiful women, who don't want someone ugly.
You also sound very pessimistic. If you don't have enough hope to try, then you can't succeed. I'm not saying, just be optimistic and try and everything will be alright. That's like saying to a depressed person to just be happy. Things are way more complicated and harder to change. I don't think one post from a stranger on the internet will make you motivated, and I don't even know if this is your issue, I can only guess. You probably tried a lot, and it didn't work, so you don't think it will ever work. And what do I know? I'm clearly not an expert for romantic relationships.
So yeah, I don't really know how to help you, and you neither, because if you know what to do, you will do it.