Dealers have been saying this forever to keep their service departments busy.
I have the hybrid, and the only thing I won’t touch is the hybrid battery. Everything else is totally doable if you have some experience or watch a few YouTube videos.
There’s a YouTube video for everything. 
I’ve watched a bunch of maintenance videos for the Maverick.
Focus ST owner here, and I’m at 80k miles. These are some of the easiest modern cars to work on—at least for basic stuff.
I do all my own maintenance—trust issues with mechanics. Just did an oil change, super easy. Also saved me $50. 
Search YouTube, watch a video. If it looks doable, go for it. That’s my method.