The fact that you are willing to admit that you aren’t a perfect writer means that you are much, much better at it than you think you are.
I will always, always, ALWAYS say that a writer who knows they aren’t perfect is a thousand times better than one who thinks they are. A writer who thinks they’re perfect won’t try to improve. A writer who knows they’re not perfect will even subconsciously try to get there, and their writing will be better because of it.
My advice is hang in there. Maybe slow down a little if you can. Do NOT stop writing, but write as little as a paragraph a day if that’s what it takes. Just keep yourself writing, keep chipping away, and eventually you’ll look back and think “wow, I’ve improved so much.”
And this is probably the most important: DO NOT LISTEN TO THE HATERS. I can’t tell you the number of hate comments I got on one of my fanfictions that almost made me stop writing. In the end I realized that hate can be good, because it gives you something to beat. Once you’ve written more, you’ll look back at that author pointing out all of your mistakes and go “Well, you couldn’t stop me from writing.” And you’ll keep going and you will be AWESOME at it. Honestly, unless that author was reviewing your work professionally and from a critical mindset, blow it off. Some authors will actively hunt down any little error in another person’s work so that they feel better about their own. Use their hate to fuel you- those mistakes you say they’re right about? Now that they’ve pointed them out, you can easily see what you need to work on, and you can focus on that instead of the aspects of writing you’ve already mastered. I promise you, that’ll help your writing improve more than anything- find your weak spots and armor them up.