Consider it a necessary, but not sufficient, start. Right now, getting rid of a teacher that is committing actual crimes is a challenge in many places, getting rid of a teacher who merely objectively doesn't teach to any standard you care to name is a challenge everywhere. You can play with all the other knobs on the system you like, but until you change this you've already lost.
I would argue that exactly because of this fact, the blundering around the rest of the system has done is the expected result. No matter what the system does, this means the problem just gets worse every year as more dead wood is accumulated. Therefore, the system never gets any feedback about the value of what the changes were. When everything uniformly produces the same negative result, you can't get any information from the results. (At least human systems are less prone than individual humans to learned helplessness and things are still being tried.) Until you fix this problem, the question of what changes actually work can not even be properly asked, in a way that can actually obtain useful and actionable answers.
(I have simplified this for internet-debate purposes; in fact some schools sometimes manage to improve, there's always variations, etc. But I don't think I need to go too far in defending the premise that the system as a whole has been sinking for decades now.)