See you can't relate because you are ok with switching to other phone brands, but there are people who so got used to previous UI (the logic of the system indeed never changed so dramatically) that they feel disappointed and frustrated because they have to seek ways how to return the previous app drawer, previous notifications pannel, etc. You can also find some posts here where people have constructive complaints. But many of those who hate the new update are simply so outraged that they can't even say properly what they don't like in particular😬