I'm always interested to hear a coherent argument against something that appears completely natural and obvious to me
Free blockchain space for everybody is neither natural nor obvious. The so called "classic" fork is not a solution. It is merely kicking the can down the road approach that makes future solution even more difficult to find.
I'll stick to Core and bitcoin main branch. Good luck with the classic free-money-to-everybody!
You could stick to Core till the fork, after that, you will need to use a client compatible with big blocks, the other chain is going to die quickly.
It'll be good if big block fork finally happens. Bitcoin Core will finally clean itself from viruses and government sponsored actors.