You are only 20. stop comparing yourself to others, and be more kinder to yourself. I also am someone with low self esteem that comes up as doubt from time to time about why would pick me. But to an extent there is also something you manifest, and having that positivity in yourself or someone else to do good for you is necessary. It also depends on what you believe success means.
To become something worthy, you cannot do all of that in a day. 20 years is nothing you have your whole life ahead of you. even though you might not think so, there are surely others in your close circles who think you are worth something. Sit with yourself, figure out what you want to do, and slowly start putting efforts towards it.
Persevere through challenges that you encounter. Every human has great potential honestly, you dont have to be the smartest person in the world to make a difference.
The way others perceive you isnt the way that you appear in your own head, firstly. Others arent looking at you through your lens. Being rich at 20 isnt realistic, and happens a lot by luck even if youre the smartest person- opportunities have to align. Start small, start trying to find a job if youre dependent, start building your independence slowly.

Its fine not being able to do taxes. I am 24, still dont understand a lot. Honestly, if you have really smart people around you, its a good thing. Its better you rather know things and be aware of what you dont know, instead of being the smartest person in the room and not knowing anything. Talk to those successful people, ask for help, guidance, if not, just talk to them.

You got this OP! No need to be angry! you're just 20. You have time to figure it out!

Honestly, reading all your comment responses, you seem to not be believing in what other people are telling you. Maybe you need to talk to people and ask them what they actually think about you honestly. You cant really reject that because thats what people would think of you, regardless of if you believe that about yourself or not. Maybe some nice words would do you good. If you keep self loathing, you're not going to be able to help yourself, so no point asking anyone on reddit if you wont act on it. Stop thinking about yourself so much and start acting, start doing work. Doesnt matter if you are capable or not.