Hulk and Thor, in the early MCU, certainly had their issues, although people didn't fully grasp then that they were seeing this gigantic universe unfold. They just thought they'd seen mediocre Hulk and Thor movies. The next 10 years certainly earned them plenty of goodwill.
I think they also bought themselves some time with the Disney+ stuff serving as a bridge between the two eras and going over as well as it did. People have an idea of where this is going now, so they'll probably be more patient with any lesser chapters of the saga. I just wonder if they have three or four clunkers in a row, or if they don't deliver soon enough on some of the big expectations for Phase 4 (namely the Fantastic Four and X-Men) if people will start to turn on it like a TV show that tries to limp on for a couple more seasons after its biggest stars leave.