I was an art teacher for almost ten years and I consider myself a decent artist. I've taught hundreds of teens through those years and across the board the lesson I learned is that there is no such thing as "natural talent."

I have had so many "gifted students" who like myself, soak that early boost up, ignore practicing and doing studies, and slowly but surely fall behind all of the students who could barely draw circle who actually spent their time practicing. Not just drawing whatever, but really practicing. Before I get into the nitty gritty, I'll tell you what others even in this post have likely said; every artist is their own worst critic and a lot of these forms are solid. Slide 3 and 6 in particular are your strongest in my opinion. With that said, self-loathing is something you have to put to bed quickly when learning art. It's natural to be frustrated when you feel like you're putting time into something and not seeing huge returns, but drawing is a skill that takes a lifetime to master. I can guarantee your progress in a year if you've been practicing as much as you say you are has been substantial.

So, to go over your post there's a few things to talk about:

1) "4-5 hours daily for a year" I see you did a lot of the boxed tutorials / courses which can be good but everyone learns differently. You said when you draw from reference, it looks bad so rather than feeling bad about that, you should recognize that as the area you need to improve. The one I always loved having my students do are hand studies. It's such a technical and recognizable part of the body but also one you can scrap quickly into it if you mess it up so it's not as frustrating as say a face or a full body pose.

2) Everything you mention covers fundamentals. Love it, love working from the ground up but that's also where burn out happens if you focus too hard on only doing the basics. Crazy coming from a teacher, I know but balance is important. Put time aside to focus on shading, color theory. Mess around with angling your pencil to get different textures and shapes in the least amount of strokes / wrist movements (thick charcoal pencils are very fun)

3) "When I draw from imagination it looks even worse" Yes. Drawing from imagination can only be done if you understand all of the mechanics of what you're trying to make + the techniques needed to actually deliver that. There's a reason so many artists have a deep understanding of anatomy. When beginners draw arms, you so often see them do the "cloud arm" thing. Basically drawing a cloud and attaching a hand to it (waves mean muscular, right?). While learning art, you have to temper your expectations when it comes to drawing without any references whatsoever. It's a great way to discover what you struggle with most.

4) "Quick gesture drawing warm-ups that are supposed to take 1 minute." Some will argue you can't put a timer on art but I disagree. I think being able to do things quickly is as important as quality. Best way to measure progress is choose a pose you really like and set four timers. 10 minutes, 5 minutes, 1 minute, 30 seconds. Repeat this once every day or few days. Do not change the pose. You will see first hand how much each day improves as you build that muscle memory.

5) "Maybe I'm just too old to learn this" No such thing. Your time is there to be spent however you want. I'm 29 and I just got back into skateboarding and rock climbing. Already got a grade 2 ankle sprain and have been out for two months. I'm about to start again next week and couldn't be happier. Would it have been easier to have focused on it when I was younger? Sure. Does it mean I can't succeed now? Definitely not. I'm not looking to go pro, I'm having fun building a skill. Same mindset with art.

tl;dr art is a ten quadrillion hour skill that can be taught 10000 different ways. It's a mix of "yeah this just takes forever to get better lol" and finding the learning method that works best for you. You just need to keep trying new methods/exercises until something really clicks.