You may refuse to fly on 737 Max, but how do you feel about 737-8200? Boeing will likely not use the "Max" name when the plan is put back into service. See: https://www.bbc.com/news/business-48995509
It may bring down the Boeing entirely, together with the operators who use Boeing aircraft. "If it's Boeing I am not going" can turn into a real thing, drastically reducing the occupancy of the flights. These businesses operate on thin margins, not being able to fill the aeroplanes may give rather short runways before their collapse.
Common, successful marketing: If a brand is poisoned, distance yourself from the name & rebrand. At its extreme, it is used alongside phoenix company tactics.
It works, although a (likely minority) customer portion will keep their finger on the pulse.
I am not an industry insider but my understanding is the vast majority of the flying public simply does not matter. We are flying on the cheapest possible ticket. The people who do matter imo are those who are flying on a corporate account or better yet those who control a corporate account. If wealthy people refuse to fly on this death trap, I think airlines will listen.
This also means that once Boeing gets the 737-8200 (or whatever) approved for flight, it will be unnoticed for customers who won’t ever notice the difference between it and an 800 or an A320.