Given that the theme of this series is Steven trying to cope with all the people in his life moving on with their lives how are they going to maintain the Steven Only Perspective with everybody leaving Steven's perspective?
Shep got a lot of mixed responses when they were introduced. They've been dating Sadie for two months thus driving a stake through the heart of LarSadie. They understood Steven's emotional issues and resolved the plot despite only having just met Steven. Sadie has left The Suspects to pursue a musical career with them beyond the confines of Beach City. All this makes Shep look like a deus ex machina thrown in to resolve the plot rather than being an actual character. Shep would have likely received a warmer reception if we had seen Sadie and Shep meet and watched their relationship develop. This would require that the show let go of Steven and allow focus to shift to other plot events or characters.
With the Steven Only Perspective in place we will never again see any of the people that have moved on unless some excuse is contrived for Steven to run into them. As these characters mature and travel out into the world they will have little to no reason to be hanging out with a 16 year old kid. Even Connie seems to have found better uses for her time than hanging out with Steven. These are interesting characters having interesting lives and we won't get to see any of it because we're stuck watching Steven and his emotional crises.
If Steven Universe Future isn't a limited epilogue and was a full serialized sequel ala Alien Force/Ultimate Alien then we could have at least have 5 seasons of it exploring what others are doing but alas!