if you're saying where we're going is Moon, then how can a 1MB cap (assuming SC or LN take a year) even with wallet fee capability, result in a smoothly adjusting fee increase as we consistently hit the 1MB cap? if anything, it will go parabolic in a chaotic fashion and result in extremely poor user experience and subsequent rejection.
Because it can be economically expected that most transactions now are low priority, since fees are cheap. This means the actual transaction volume that likely would be taking place given only somewhat more expensive fees is much, much less. It's should be obvious enough that if transactions were completely free people would spam like crazy. That's not a judgment on the validity of those transactions; it's just economic reality. People start to economize dramatically when there is even a marginally-above-zero cost versus when there isn't.
This is in no way suggesting 1MB is sufficient, but it's not helpful to pretend that transaction volume when fees are negligible will remain the same if fees go to merely tiny. In no other market would we expect such a thing, and for all we know we could easily be talking about order-of-magnitude differences in volume from a fee increase that still presents no real pain for any major use case.