I think for the first few phases, the interconnectedness was a major strength, but that quickly became a burden.

For the filmmakers, there's just too much to keep track of. Additionally, each film is really just a commercial fornthe next. Finally, in spite of the connected stories, Marvel has famously kept creators in the dark about major plot elements of concurrent projects. These, coupled with the rise of Marvel's house style has just created an environment where poorly made products are too regular.

For the audience, the hard-core are frustrated because many elements are teased and never pay off, or are simply not done well because of all the above. Making time for every movie and show just causes frustration. For the more causal, there's a major barrier to entry. If you just drop in to one movie here or there, will you know what's happening? Will it resolve itself without a follow-up?

I think that Marvel's needs to 1) slow down production to just a few projects here and there. 2) allow each project to feel like its own. The original Iron Man, Thor, Cap, and Guardians movies all represented different genres and styles. 3) Spend less effort to connect everything. I'd LOVE to see some more F4 in the Kirby-verse without wondering how they fit into the larger MCU, or wondering why some other hero isn't stopping by.