For me the case is much more simple. I wouldn't say the best PES every etc, but IMHO both PES 2020 and 2021 are very good at producing a solid output with less complicated inputs.
The previous PES games, 2019-2018, tried to produce a more complicated output, with the higher response in control-dribble, but the results are more inconsistent football-wise.
I really don't know how to explain it, it's like 2020 and 2021 try to sum 1+2+3 and the result is usually 5 or 7. 2018 and 2019 try to sum 10+20+30 but the result, instead around 60 it is 100, 20, 90 ,15, etc....
I mean the most recent 20 and 21 have two basic functions, passing with

and some type of dribbling, which is rigid a lot of time and feels stiff and unresponsive. In the 18 and 19 versions, if you isolate the response with L-stick, 2018 tears appart every other game, and then 2019 tears apart 2020 and 2021.
All of the above games , have some fundamental flaws of course.
I don't honestly know how to explain it, some times it is better to promise 20 and do the 10, than promise 100 and do the 10.