It's pretty easy to say something published is crap. (And some are.) It's pretty easy to discount all the work that went into it. It's pretty easy to imagine we could have done it. But we didn't.
If you can show me a single language where prescriptivism has prevented linguistic drift or mitigated the need for footnotes in texts that are hundreds of years old, I will gladly use a time machine to go tell Saussure he was full of crap.
Trying to "make it" as a writer (or really as any kind of artist) requires a certain level of dogged faith in oneself. Not the blind hubris that you are an unsung genius, or the delusions of grandeur that prevent you from acknowledging criticism or noticing that no one likes your work, but simply the belief that you have something worth sharing and some people are going to enjoy it if you can just find them and they can just find you.
Life is too short and success is too uncertain to worry about trying to write what is going to sell. Write what you're dying to write.
The prose of writers who "don't like to read" is extremely self-indulgent. It reads a little bit like walking into a social group that uses a lot of inside jokes or one with echo chambers that don't permit contrary opinions.
It's okay if you want to verse yourself in a version of English that has fifty to a hundred years worth of anachronisms in it. That's kind of cool actually. But if you insist everyone else play by your rules and act like a real asshole if they don't, your fortune will be to die alone.
The only real mistake you can make is to quit.
If you're ever unconvinced that linguistic prescriptivists are similar to religious purists, pay attention to just how long it takes them to call someone doing something they think is wrong a "heathen."
Before a writer who wants to be a "successful writer" (be it famous, rich, or just paying the bills with writing) embraces a rationale for not writing daily consider this: as difficult as it can be to become a successful writer who writes every day, how much more difficult must it be to become a successful writer who doesn't?
Most writers block is performance anxiety. When you truly accept that the first draft is crap, you get over writer's block pretty quickly.
High school grammar is....well it's like a lot of things you learn in high school. It's basic. It's very fundamental. It's an important start. But if you think that's all there is to it or you that you've gotten the whole story, if you can't learn to accept any new information, or even if you just think every high school learned it the same exact way you did, you look pretty foolish.