How can anyone who has seen those episodes claim that Mando/TROS invented Force Healing (even resurrection!) out of the blue.
I don't think the objection has anything to do with "inventing" Force healing; that ability already existed in the EU long before Disney Wars, and even before TCW. The problem (only speaking for myself) is introducing it into an existing story with an established context of what Jedi were capable of, even at the height of their powers (the PT era).
By having a baby who can barely walk or talk use it, then by having Rey use it with only a fraction of the training of her predecessors, there's a natural set of questions that beg to be asked because of how inconsistent that is with every previous SW movie.
If a baby Yoda can use the power instinctively, then shouldn't the 900-year-old Jedi master Yoda know this power? If a desert scavenger with a year or so of informal training can do it, shouldn't the "Chosen One" desert slave with Yoda-levels of midichlorians and 10+ years of Jedi training know how to do it?
In Mortis, those characters were basically gods. What they're capable of doesn't mess with the saga that we see playing out in the movies where Jedi *aren't* gods. But if in the movies, Rey and Ben can suddenly do something that would've definitely been used in previous films during key plot moments, that's a different issue with a unique set of consistency problems, IMO.
For me, you can't have Force healing be such a common and easy "trick" to learn and use without sacrificing drama, tension, and stakes going forward. And using it now with characters who seem to be doing it instinctively just makes it all the more problematic that it wasn't used before.