Marvel is only studio where they budget re-shoots at a very high level even before they start shooting. Their reasoning is that their stories are a bit "high concept" and given the volume of movies they produce each year, they are pushing the pre-production teams to their limits. In short, they spend less time on pre-production planning than they should for the size and scope of movie that they are producing and prefer to just "fix it in post" should the edit not come together the way they expected. This plan works when each movie is a blockbuster as they were in Phases 1 to 3. So, if each movie is generating hundreds of millions in profit, then would you want to only produce one a year and take the time to plan it right or pay $20 to $30 million more in post-production to fix the edit so that you can get two blockbusters out the door each year.
Unfortunately, Phase 4 was (IMHO) a dumpster fire for Disney Marvel. "Eternals" was too long and confusing. "Multiverse of Madness" was just a confusing mess built on a weak premise that even Sam Raimi couldn't fix (really...she gets scared by a bee and can now cross multi-verses? Are bees that scary? Is that the best they can do?). And "Love and Thunder" prompted a "What were they thinking?" type of response because it violated every concept of the "hero's journey" essential to good character development. It also made Thor look more like the village idiot than they have done in previous movies (which I think prompted Chris Harmsworth's pledge never to work with Taika Waititi again). "Spider Man No Way Home" was the only movie that actually lived up to and exceeded my expectations for good story and character development that we saw in Phases 1 to 3. Unfortunately, the deal between Sony and Disney over the Spiderman rights ended with that movie. Who knows what happens next.
So that VFX reel proves to me that they are not even trying to do good pre-production anymore. We really don't know what the VFX will look like through the windows so let's not even try to match the lighting on set.... we'll build the whole room in 3D and fix it later (imagine if they had done some pre-planning and shot that set in a Stagecraft Volume). Where does the actor stand? Ahh...put him here, and if we don't like it, we will fix it later. Did we make a prop book? Whoops --- didn't have time. Here, hold this piece of cardboard -- we will fix it later.
It may not have been as sloppy as that, but you get the idea. That "we will fix it later because we have the money" mentality keeps a lot of VFX houses employed by Marvel. Marvel's movie revenue for Phase 4 is not where Disney wanted it to be and did prompt this rumor on Phase 5. So that thinking may change.
Dave