I just find squats hard. Is it something in my technique, or am I just weak?

https://youtu.be/crM1e32LpZA

I have my heels raised slightly using some plates because I feel I lack ankle mobility to get past parallel otherwise. This was also my last set, so my quads were burning here already. I maybe just don’t squat enough (+/- once a week and sometimes I do skip a few weeks) to actually improve.

I find squats quite scary, mostly because I seem to lack stability (see rep nr 2 - the raised heels already helped a lot with this, but obviously not 100% there).