If space in a block is not a limited resource then miners won't be able to charge for it, mining revenue will drop as the subsidy drops and attacks will become more profitable relative to honest mining.
That's why transaction space should IMO be scarce. But not hard limited.
A hard limit cap will just make a transaction impossible at a certain point, no matter how high the fees paid. If we would have 1Mil. legit transactions a day, with the 1MB limit 400k would never be confirmed, no matter the fees.
A algorithm adjusting max. blocksize in a way that transaction space remains scarce, but ensuring all transactions can be put into the blockchain is IMO a reasonable solution.
Ensuring fees would always have to be paid for fast transactions, but also ensuring every transaction has a chance to get confirmed.