The 21M limit is not fixed because Maxwell is protecting us from changing it, the 21M limit is fixed because the majority of users are incentivized to keep it.

It is the same with the blocksize limit, the majority are incentivized to increase the limit, so it will be increased.

Toomin is stating a basic truth of bitcoin, bitcoin is whatever its users want it to be. And the beautiful thing about bitcoin is no one can stop that