1). On the topic of having to see all the movies... you sort of can start fresh once Phase 4 begins. Not completely as there will be sequels, but with the addition of many characters and no vast, overarching story anymore, it's easier to just jump in.I'm guessing it's something along the lines of the doing 3+ movies a year thing until people stop caring. IE . - riding the horse till it falls to the ground. People are already saying we have too many Star Wars movies and they are just doing one a year of them. Granted, the MCU is different story lines, but it's really one big story where you almost have to see them all to understand whats going on in an Avenger movie.
Theres also the effect that Scott mentioned. Where do they go from here? They are cycling out their big stars and are throwing new ones out. Will people accept them? Will the movies be as well received? And will they just keep throwing movies and new characters out there regardless? I go see every MCU movies in the theaters, and I'm not real excited about whats coming up other than GOTG. I'll still go see them all, but at what point is too much, just too much?
2.) Yeah, there's 3 MCU movies a year, but also think about how prior to this year, there had routinely been 5-6 Marvel movies a year when you count output from FOX and Sony. With The only X-Men movie left to be released New Mutants, X-Men will be sitting silent for awhile and even once they come back, they'll likely be back under the MCU brand, meaning the overall output of Marvel movies won't be as high.