The current situation is that
a) both Bayern and Dortmund came out publicly to denounce the Super League and promise not to join them. Noone asked them to do that.
b) unlike other top 5 leagues the DFL follows a hardcoded licensing model. Clubs need to reapply for a league license before every season starts and fulfill every criteria to start in the 1st or 2nd division. The criteria also requires that you cant be part of a foreign tournament. The license statute cant be changed unless the DFL which consists of the 36 clubs of the first and second division democratically approve it.
c) a breakaway into the ESL would require membership votes. It's too big to be decided by the chairman alone. Also regarding application for membership via internet. Yes you can do that, but the main perks of a Bayern membership are prioritized ticketing as its almost impossible to get a Bayern ticket with 250k applicants for a 75k stadium and members get first buy options (and even then there are more members than season tickets available). Not something a dude from the US or India would typically be interested in, at least not enough to really have a big outcome on such votes.
The owners of memberships are almost entirely match goers and ultras. Since you know a thing or two about German football culture, you can probably imagine what these people are like. Also actually voting FOR the breakaway into the ESL also means 50+1 wouldnt apply to Bayern anymore. So members would essentially vote out their own grip on the club which would be quite paradox.
This is why I dont believe in it. And why I fancy the chances of seeing KingLeo10 with a Bayern badge by 2024.