I don't see how. Please explain how consensus around increasing the blocksize is ever going to happen?
This is circular reasoning.
If a majority can agree not to increase the blocksize limit, then that is a consensus decision by definition. The logic wasn't "no increase, because Bitcoiners say no to everything, always". The logic was "no increase, because it's the wrong decision at this point in time, for design reasons".
My point is that there will always be people that don't want to do X, which means the result will be getting an altcoin, and the legacy chain will go on.
When a case is made that makes sense to the majority of Bitcoiners, they'll accept a blockweight increase. For instance, Segwit was an increase in blockweight, and Bitcoiners accepted it. So it's already happened, saying "it's never going to happen" is a difficult argument to sustain given this reality.
Segwit was not "accepted by bitcoiners", it was accepted by some bitcoiners (again my point, total consensus is impossible), others didn't accept it, which resulted in BCash being created, but this was a soft fork. If a way to get segwit via soft-fork was never found, it would have either never happened, or we would have Bitcoin and Bitcoin-segwit in a separate chain (which some would claim to be Bitcoin), and so on.