Main Street Theatre was announced and canceled years before anything for the EPCOT overhaul was greenlit. You might be confused with it being part of the same presentation that announced Guardians for EPCOT, which was a wholly separate project from the wider park overhaul that was started a few years later.
Covid was a factor sure, but I never believed we would see that festival building even before covid. If something looks too good to be true I think it's a good rule of thumb at this point to believe it is. Maybe this cycle of announcements will prove that wrong, but there's a lot of precedent to back up the skeptics.
The EPCOT projects really weren't that long ago, and they weren't what established the precedent of Disney canceling projects. It becomes kind of a boy who cried wolf type of situation, if the company keeps telling you they're gonna do something and then they don't do it, it's natural to expect them to not do the next thing they tell you they're gonna do. Maybe this announcement cycle will break that precedent, but as of now there's little reason to have faith in the projects they've already shared little about.