To quote Colin Powell in regards to the Invasion of Iraq: You break it, you buy it.
It's easy to be sitting behind a keyboard and suggesting regime change, but another to actually be doing it. It has a number of high risks. One of them is rallying indifferent members of a population in support of the leadership against the invaders. Whoever would succeed Putin would have a major benefit when stepping in—an energized populace, and valid excuse to rearm.
Invasions and occupations are a major endeavor. How well did Iraq and Afghanistan go for the US, and so far, Ukraine for Russia?
Yeah; that's a lot of work.
Better is to just bomb the shit out of Moscow/St. Petersburg until Putin either kills himself or goes into exile or one of his generals kills him or at least pulls troops fully out and gives Ukraine back all the land.