As others have suggested, you need to, at some point, just write. Research is cool, and can definitely enrich a story, and you need to have an idea of how your world fits together. But I don't think you need to, say, fully understand the principal macroeconomic theories underpinning your imaginary world's financial system in order to have Bob pay Ralph five rupees for a catburger.
World building can be a means of procrastination, if you're not careful. What you might consider doing is just say fuck it and start writing the story. You have an MC and you have a general idea of the main plot arcs? That's plenty, if you want it to be. Start writing with that. If you get to a point where you feel you can't write a realistic scene without establishing the history of the Wood Elves and how they were oppressed by the Tawnee Goblin Tribe of the Flurgle Mountains? Just stick in a note that says "stuff goes here" and move on, or just throw in a placeholder reference.
Right now, you're probably spending hours developing facts that will never even be referenced in your book. Which is fine to a point, if it gets you to better understand the underpinnings of your world, but it also means those could be hours of work that are of zero value. If you can get a draft of your story, or even part of a draft, you'll have a much better understanding of what information you actually need to develop. Hell, maybe you'll wind up axing the Wood Elf arc altogether, and it doesn't matter what the damned goblins did to them.
Basically, there are always a million reasons to not write, and you listed several - the world isn't developed, you're not mature enough, whatever. At the end of the day, you need to set those aside and just do it anyway. It can be scary as hell to start a new project, especially an epic fantasy novel, but once you get past the first 1000 words, the hard part is over. Okay, one hard part is over.
tl;dr: Shut up and write.
(Also, I know a few 20 year old writers who are better than I will ever be and create some amazingly nuanced stories that belie their tender years. Age has little to do with anything; it's all about practice.)
World building can be a means of procrastination, if you're not careful. What you might consider doing is just say fuck it and start writing the story. You have an MC and you have a general idea of the main plot arcs? That's plenty, if you want it to be. Start writing with that. If you get to a point where you feel you can't write a realistic scene without establishing the history of the Wood Elves and how they were oppressed by the Tawnee Goblin Tribe of the Flurgle Mountains? Just stick in a note that says "stuff goes here" and move on, or just throw in a placeholder reference.
Right now, you're probably spending hours developing facts that will never even be referenced in your book. Which is fine to a point, if it gets you to better understand the underpinnings of your world, but it also means those could be hours of work that are of zero value. If you can get a draft of your story, or even part of a draft, you'll have a much better understanding of what information you actually need to develop. Hell, maybe you'll wind up axing the Wood Elf arc altogether, and it doesn't matter what the damned goblins did to them.
Basically, there are always a million reasons to not write, and you listed several - the world isn't developed, you're not mature enough, whatever. At the end of the day, you need to set those aside and just do it anyway. It can be scary as hell to start a new project, especially an epic fantasy novel, but once you get past the first 1000 words, the hard part is over. Okay, one hard part is over.
tl;dr: Shut up and write.
(Also, I know a few 20 year old writers who are better than I will ever be and create some amazingly nuanced stories that belie their tender years. Age has little to do with anything; it's all about practice.)