This. Although using them in between two keyframes that are far apart are bad, you can achieve effects that transitions could never do by grouping together keyframes with linear transitions.
But on to my two (or more) cents:
I would have to give an upvote for effort here, not anyone can just make an 11 minute animation
Some text should have more time on screen so we can read them without having to pause the video.
If your computer allows, darken the scene and try using lights (Torches, Glowstone, etc.) to illuminate the scene.
For the starships, I would recommend using Hardened Clay instead of Diamond Blocks (but it's already too late)
When the camera zooms around the island, I would recommend putting the camera in a folder inside a folder inside a folder, etc. and move said folders around so that the camera moves much more smoothly
If you haven't already done this, for any future endeavors, split the movie into smaller chunks of projects (Different scenes should have their own project)
As much as walking cycles could be improved, I'm not going to bother with them here (They take a long time to nail perfectly, longer for non-human creatures like Endermen)
Yea don't bother using text to speech voices if you don't have voice actors. Use text like you did with the Endermen.
Remove any and all fog when in space scenes like the one you have