What I think you're missing is that the disclosure could come from a bad person who doesn't care about any of your arguments. It's like I'm saying "banks should invest in vaults to protect against theft" and you're saying "that costs money and disruption of building work, what if you just don't talk about where the money is kept". I agree that if people didn't steal the money, that would be nice. But most of the people who are talking about where banks keep money with a view to stealing it, aren't going to shut up in order to keep the money safe, because they don't care about keeping the money safe. So if us bank customers stop talking about it, a) that doesn't keep it quiet, and b) our money gets stolen.

It would be a nice world if we could tell companies about flaws and they fixed them, and nothing went public, but instead we tell companies with "responsible disclosure" and they ignore it, don't spend any effort on it, act incompetently leaving it with first line support people who don't understand it and have no path to escalate it, have no security contacts available for reports, cover it up or deny it or try to silence it with NDA style agreements, prioritise shareholder profit or public image over it, and generally behave irresponsibly in all possible ways that avoid them having to deal with it, with very few companies excepted.

In light of that, public disclosure with all its risks, actually does kick companies into taking action, and closing risk vectors for good. Like companies who say "we put customers first!" but it takes a complaining public Twitter thread for them to even respond at all. Telling people to not take it to Twitter ignores the fact that there's no other way which seems to actually work.

Give an alternative which also gets problems fixed, and I'll be much more in favour of it.