Why is anyone even still talking about this?
In my case, because with a gigantic chain size, decentralisation is at risk (see above regarding costs etc).
The price of transactions will no longer be a cheap $1 or whatever but that's okay because doing on-chain transactions will be sort of like wiring money is today, something you don't do very often. On-chain will be just for large transactions where the tx fee is entirely negligible, or moving money around, while everything else will be done on Lightning or possibly other later developed L2's where you pay like a penny for a transaction. So it'll be alright for users.
This scares me. What you're describing is mitigation by centralisation, forced trust and forced custody. Unless you're proposing that every user should run her own L2 node, in which case we're back where we started (prohibitive costs).
And for miners it'll be fine because by then miners will almost entirely be using either essentially free stranded energy (startup cost but then extremely low maintenance cost for renewable energy) or they will be mining companies who are tied directly into power plants (which is already being done today) to strengthen the energy infrastructure of society while also getting super cheap energy for mining.
Unfortunately (in my view), this separation between "users" and "miners" already is a fact. The original reason to use proof of work instead of simply counting IP addresses (to determine majorities) was to mitigate the fact that certain actors are able to allocate huge numbers of addresses. The scenario you're describing is magnitudes worse but not at all unlikely, I'm afraid. It's not really the topic of this thread though (but very related, I agree).