10k hours and still the same MMR I calibrated at. Whats wrong here?

So I started playing Dota 8 years ago with absolutely no knowledge of the game, or MOBAs in general, and have after all this time learning heros, game mechanics, items, builds, matchups, watching countless hours of videos, streams, all the TI's, I am still 1.5K MMR.

I have been a competitive gamer my entire life (37), and have never played a game I took seriously and sat at a 50% win rate. I have never played a game I didnt take seriously and sat at par, yet in Dota I can not climb to save my life. I could understand if I was peaking for my skill at like 5-6k where things become absurdly intricate, but im not, Im at 1.5k where players are absolute dunces.

There is no video you can suggest I havent watched multiple people speak on the topic. Proper lane mechanics, rotations, securing rune timings, roles, counters, power spike timings, item timings, unfavorable matchups, favorable matchups, kill lanes vs defensive lanes, meta heros, meta items builds, minimap awareness, priority targets, orb walking, how to properly farm jungle, the importance of pushing dangerous lanes with heros who have built in escapes. Name a mechanic, and im sure im fully aware of it (may not always implement it, but I have the knowledge). Yet all this knowledge from when I started and was absolute DOGWATER, has earned me a net zero in MMR and according to the system, I am the same player I started as.

You would think that after 1000 hours of just learning the heros and their abilities, I would climb even just a little, but that is not the case. Let alone all the other things you learn while playing Dota for this long. None of it has caused me to differentiate myself as a player from the players I was when I knew nothing.

Over the years I have been accused of smurfing, laned mid against smurfs and asked them whats wrong with me, and having them tell me I play way above this bracket and I will be out of it soon. I dont think I should be 7k mmr, I cant tell where I sit at this point, but there is just no way Im the same from when I started. I dont get it. People try to tell me "oh, well your moving yp in skill at the same rate as everyone else in your bracket, but I dont buy that, as my bracket is filled with brand new players just starting their MOBA career, and then also a lot of SMURFS LOL. I never complain about the SMURFS, I dont find they did anything special but identify a very weak player on my team and crush them for easy farming, obviously they are more skilled than everyone, but my mind isnt blown I can see how and why then are winning.

Is the system flawed? I often feel like I am forced at this win rate. The streaks in the game make me believe so, like they let you win easy games (boring), they you get some evenly matched (fun), then you get 8 games in a row where you can believe how bad 3 of your teammates are. Having 2 games in a row where your you have bad luck is one things, suddenly the same type of player for 10 straight games doesnt seem random. Is it because I use to have a terrible behavior score? Is it because I have multiple accounts? I dont know, but something must be off with the way I play, because its been 10k hours of no progress, and I can tell you I was absolute TRASH my first year of Dota.

Help me learn the ways of MMR gain, because im stumped.