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While it is nice that these major blockbusters can feel like events and people can tweet about it in unity, I'd argue that is also a good reason for a theatrical window: because people have absolutely no restraint with posting spoilers, or consider someone may be watching later.
What happened with WW 84 is basically the same thing that happens with The Mandalorian. I don't watch that show, but I know most of what happens in it because it becomes deluged over my feed immediately after airing anyway. I'm lucky I don't have any interest or it'd be ruined.
There is this culture of "it's out now, just talk about openly", which is honestly a bit selfish. It is one thing to do that in a space where you can shield spoilers, but most socials don't do that. It is quite unfair for many non-US viewers who have to wait to see them.
The psychology is different: with theatrical, you have to pay to an appointment to see it, so the fan community feels like more of a sense to protect it. On streaming, the immediate access makes people feel like they have no responsibility to do that. They're valued differently.
