For the betterment of Atletico Madrid, Semione should be replaced with young manager with good coaching skills.
Considering how long he manages Atletico Madrid, some of their systems should be designed around Simeone so replacing him would take time. I wonder if the fans want that though. By fans, I mean those who travel and buy tickets to watch them play, not social media darlings who speak about "we are in a crisis" whenever their favorite team loses. Most of the time they're farming for views with their terrible analysis of a match.
Aiming for trophies is a good thing, especially if it's a CL trophy. The question is whether replacing a coach will magically answer that or not (probably not).
He is about to get a pay cut, so it is going to be a bit more helpful for the team to keep him for longer. He is aware that if he keeps failing to win the title, or have any good results at Europe, then paying him that much will not be ok for the team and will be fired.
So he rather gets like a long five year deal, for lesser amount of money, and he will be doing a lot better that way, because then even if he doesn't do that great, he could still keep managing since he is not getting paid absurd amount of money. He will still be paid somewhere along 15-17 million range, but not 30+ range like he used to, which means nearly half gone. I do not see any reason for the team to fire him yet neither, he is doing decent, will be better eventually.