Like a lot of people I am stuck at 20 seconds. I am currently practicing a lot, like 100 solves a day, and I am just wanting some different practice techniques/ ideas for improving. I do slow solves to work on look ahead, practice my cross with my eyes closed, and have even resorted to downloading a metronome on my phone to practice consistent turning.
I am not improving.
If this just means that I am destined to be a 20 second solver for the rest of my life, thats ok. But I will not stop trying. So any advice would be greatly appreciated.
Come on! You're the Cubeologist! I watch all your videos and you're right now just a little bit ahead of me with your PBs so, please DON'T SAY THAT AGAIN!

Well, seriously, I'm suffering the exact same issue since months ago. In fact my progress has always been slow. I started speedcubing like 18 months ago and I'm still struggling with sub-20. Maybe because I'm 44 or maybe because I'm just unskilled, I don't really know.
When I watch your videos I see your turning during LL is faster and more precise than mine so the culprit must still be F2L lookahead. The paramount of what you must be aiming to is that slow solve of 15.x that you showed in your recent "slow solving" video.
But, as smiles has already told you, there are plateaus, and the faster you get, I assume the longer the plateaus. As I said, I have been stuck at 23 (Ao100) for months but, once I studied it carefully, the plateau was in fact a slow slope from high 23s to mid- to low- to high 22s... yeah, over the course of many more moths than I would have liked to, but still a declining slope.
And, all of a sudden, the other day I finally finished working up my "gummified" YJ Sulong (too much weight 3 lube on the pieces, I guess) and it started to feel a bit less gummy. I changed from my previous main (Chilong, Maru lubbed) and, wow! I have more control and as the cube is not as fast I can concentrate better in my lookahead (and I overshoot less as well). So, in the course of this past week, I have improved my long averages almost by a second from very low 22s to low-to-mid 21s.
Somebody told me months ago in this forum: if what you're doing does not work, do something different. So, change cubes, lube them differently, change your training, change to a different puzzle for a while... Just try something different. For what it's worth, apart from the cube change I have started practicing OH, can this be helping my 2H times? I really don't know.
Sorry for the long post but, hey, I don't always have the opportunity to chat with you!!! One last thing, whatever you do, please don't stop speedcubing and don't stop doing your great videos!