why am i so bad

Do you want actual help or did you want to vent? You could head up to r/summonerschool, they have a lot of resources to help you improve.

If you're determined to climb, you could probably reach silver 5 by the end of the season or even better, given you can break your old mindset of "I'm hardstuck".

It all comes down to your attitude. Playing for years and years doesn't make you good...it gives you an understanding of what champs can do. What helps players improve over time is the desire to improve over the course of every game. Are you actually applying what you learned on reddit? If no, then start. If yes, then find out why certain things aren't working and formulate a way to fix this.