I have serious issues with YouTube on my iPad also.
I have a 4th gen iPad (A1458) and I also use a 5G wifi connection but still have problems.
I've followed all of the guides to try and resolve the issue but it still lags.
It usually starts with the quality of the video I'm trying to watch, degrading before it eventually starts to pause while the app buffers.
Why we can't control the buffering within the app itself is down to Google but surely it shouldn't be this bad.
Even when in the same room as my hub the videos still degrade and pause frequently.
Vimeo on the other hand has no such problems.
In fact, practically every other app for video streaming I have on my iPad has no problem in playing videos, unlike the YouTube app.
I'm hoping that this issue will be sorted by the time the next iOS release is here.
Surely that is the reason why we are hearing nothing about this from either Apple or Google.
I should also add that this is my internet connection speed over wifi using 5G on my iPad.