https://www.comicbookmovie.com/guar...-10-20-years-of-marvel-studios-movies-a153418
Here is just more confirmation from James Gunn how cosmic the MCU will be going once phase 4 is finished. Now, don't get me wrong, I highly doubt Marvel will completely abandon all the earthbound heroes in lieu of the cosmic ones, especially now that Spider-Man is working strong in this universe. However, there is just only so many earth-destroying stories that can be told here on earth before the audience gets tired of them, especially after a big 2-movie event like the Infinity War movies. Therefore, my guess is that we'll see at least 1 cosmic movie come out for every earth-bound movie after phase 4. There is just so many more directions things can go for Marvel now that the cosmos are open.
Also, I think the scale of most the earthbound movies will get tapered back quite a bit to try to avoid that earth-ending audience fatigue. One thing Spider-Man Homecoming did well was prove that the scale doesn't have to be huge in order to keep the stakes high and the audience on edge. Its amazing how big the stakes can feel with the smallest of scale, simply through good acting and storytelling. Also, if Spider-Man is the focal-point moving forward, most Spider-Man stories in general have much more street-level stakes than what the typical Avengers story has. In fact, in that way, one could argue he fits better into The Defenders in some ways than The Avengers (one can only dream of a crossover).
FYI... I'm still holding out hope that the MCU cosmos future somehow includes The Fantastic 4 one day. At least a guy can dream.