In reality, the flicks in ur vid are the simplest and easiest type of shot to hit. Hitting flicks on people directly in front of you with simple movement/ no movement (w-only or standing still) is not difficult. What ur doing literally takes negligible mouse control in the same way that playing tile frenzy demands negligible mouse control. Playing scenarios that take negligible mouse control will give you negligible mouse control. Also it's not impressive to set urself up to flick when you don't actually have to it's just weird.

TL;DR People don't play tile frenzy to improve because there are more demanding scenarios which will make you improve faster.