Unless you have billions at a bank, I don't see why any bank would even consider changing how their website works because of a single customer. And, well, real billionaires probably don't care about not being able to use a website on Firefox.
My bank calls me once every few months, if everything is ok, and if there are is something that is bothering me and could be improved, or if they can help with something. At first I thought it is some marketing program and some manager has to achieve some KPIs, but surprisingly, they did listen to suggestions (it took time, but they eventually did).
So you never know, if you never try.
Business account is in different bank, and the communication there was much harder (obviously by someone not trained in communication and having to talk to me as unplanned part of their job). The fees are lower, though.
So it doesn't seem to be by the amount of $$$ on the account.