Plus there is the absolute dickishness of booing a team that spent six months or more slogging their guts out so they could sing, in tune, for three hours straight, for their entertainment.
In short: it wasnt you.
I think the audience should be expected to react with their genuine feelings about the performance; if the team wants a positive reaction every single time, they're going to have to earn it.
Many studies show that improvement requires operating at your limit, and sometimes failing. Never letting anyone fail is a disservice to them in the long term.
When the seats are empty, that's the real marker of failure. But you can't get that information directly - flops are always a case of "couldn't see it coming". You can aim to derisk by following convention, but that's treading water and makes you an undifferentiated performer. You have to set principled benchmarks for yourself to excel because the feedback is going to be too sparse otherwise. That's the real struggle throughout all the arts. It's not on other people to set them for you.