Well, exactly.
If we're going to live in a capitalist system, we need to play by capitalist rules. Therefore, what judges the salary that a profession "needs" is the salary that attracts enough people to do the job (and ideally some surplus so employers can pick the best fit).
At the moment, we have a national shortage of teachers which is getting worse. So clearly salaries, workload, benefits etc are not appropriate.
I assume wildly most people on mumsnet have children who will go through secondary education. I know some will use private schools, but most private schools still need their teachers trained (in part) via the state sector, and often don't want to employ ECTs either.
So if you want your children to have subject specialist teachers, then pay needs to improve. Workload and immediate, tangible benefits (not the pension- the pension is irrelevant to a lot of younger teachers) need to change.
But then again, a lot of parents on mumsnet insisted they'd be happy to have their children taught by an unqualified 19yo apprentice recently, so....