I am what I would call a "hack".
This means basically a slight disregard for timing.
The right hand plays melody single notes with the occasional chord under that note.
I also do some triplets or Grace notes but basically that's it.
I am less than 2 years into the piano, but I have played banjo on stage. Learning banjo took longer than usual because of a lack of structure. I finally prevailed. I am moving at a much faster pace on the piano.
I BELIEVE THAT I HAVE THE EXACT ANSWERS THAT YOU NEED! I even organized the information that you need with numbers, just for fun! It is, however a list of 10 overall tips, not just left hand tips.
You aren't a hack. You may have been lured down a seemingly faster and easier path that has left you unsatisfied with your progress. You have a good foundation with some clear weaknesses that need work. Your post reminds me of my path to learn banjo.
1. Immediate gratification can't be your top priority. This will keep you engaged, but it will not get you where you want to be, in a timely manner.
2. Timing isn't fun, but you need to back up and WORK on it. Learn to play properly with other instruments or a metronome. This will mean slow and tedious work, not play. If you refuse to put in proper work, then you can try singing(with good timing!). I started singing and strumming guitar years ago. This helped me develop an innate sense of timing. When you can turn on a metronome and play properly, you WILL be a much better player.
3. Slow down and work specifically on those right hand chords. Work on being able to play more complicated partial chords with the right hand. You have the idea, but you need to back up, slow down, and improve this part. Get faster and more advanced at it by going slower for now.
4. Structure your practice. Dont sit down and play the same things in the same way every time. Back up, slow down and pick apart what you are doing. Spend a good amount of time practicing what you dont know.
5. Learn left hand chord patterns. Use youtube or there is a newer book called 100 Right hand Patterns, I believe. I'll get the name if you want. Learn two or three good movable patterns and work on them. Slowly add them into the songs you already play. Dont try to play 50 different patterns. Play one until you are sick of it and work on being able to incorporate it on the fly. This may take longer than you think. It is an important part to good improvising down the road. It can help timing too.
6. Pick one simple song that you know well and play it often. I'm sure you do this now, but slow down and learn to play it in many different way. This will include more intricate right hand work and new chord patterns with the left hand. This will keep you from getting bored. I can play songs on the banjo and not even know how I played them. I may play a song in different ways everytime, without thought.
7. Spend time practicing the left hand. Play solid chords, moving through inversions, with good timing. Focus on details, like sounding all notes at once. Know how to play the chord you want in multiple ways instantly. The left hand is important and shouldn't just follow the right. Go back to left hand basics and learn from there.
8. Watch other people play.
9. Don't go too far in the other direction. Dont become so structured that you lose enjoyment. Balance is the key.
10. Buy a better instrument. Ok, this may not be good advice, but it always makes playing more fun and interesting!
Let me know what you think of my list!