you arent as bad as you make out to be lol. We are all trying to get better
The main advice I could give would be that doing the WHOLE SCALE is like the hardest way to learn IMO. So if I were you id break it down into smaller sections
for instance maybe small repeatable sections like this:
triplets or sextuplets
6 notes up then slide up one position and 6 notes back down etc. Thats one way Paul Gilbert showed on his old Intense Rock vid
thats an easy pattern that repeats and you dont have to worry about your pickstrokes or pickslanting. just keep your UWPS etc
Then you can experiment with stuff like varying the tension in both hands etc. A little firmer, or more relaxed or whatever and see what feels good as you try to speed up
It does look like the left hang fingers are sort of flapping around a bit excessively. Others can chime in with their advice on that but maybe start trying to get the motions a bit smaller and more controlled…in other words you dont have to lift the fingers so high off the fretboard.
lastly, to confuse you even more. You can consider your right hand anchoring approach. Some people do “hard anchor” with the arm like you are doing. In other words you are anchoring with the arm and never moving it as you go to higher or lower strongs.
Another approach is to let the arm and hand move a little more freely as you go to higher and lower strings.
The way you are doing it with the hard anchor, you have to change other things each time you go to a different string. The wrist angles have to change or the fingers have to be manipulated. Also of course the pick angle against the strings will be varied.
I used to do it the way you are doing and I really struggled to pick the e and b strings because the angles got so weird.
If you let the whole arm and hand more freely move up or down to better track the string changes, it takes away some fo the other variables etc. You will no longer have a different wrist angle and different finger manipulations etc.
I dont think either way is “right” or “wrong” but you might experiment some the other way to see how it feels
if you take the 2 things I mentioned…1) doing the WHOLE SCALE at once, and 2) using the hard anchor and therefore having different picking angles on each string, you can see that you are trying to groove like 9 million things at once
Thats why I suggest trying smaller scale fragments, like just work on each different set of 2 strings at a time etc.
also of course you cant go wrong just working on your speed and efficiency with stuff like the 6 note pattern on one string. This will help with coordination and you can more easily focus on keeping those fretting fingers from flapping around quite as much
Triplets or sextuplets
B-----8–5--7–8--7–5—repeat or move up or down the scale etc
oh btw, its not that odd to be “struck” for several years at a time lol. You can be at one level for a while and all of a sudden you move up quickly. I had been playing to 27 years before I heard anything about pickslanting. I was a pretty good player but I never could do stuff like 3nps scales lol. Now I have worked on the various pickslanting options and it has really helped me become WAY better
So dont get discouraged