Basically the Gen 7 games, especially Ultra Sun and Moon, reveal it's... not such a great thing. At all. Now, it's not necessarily harmful for all of them, but there are a few messed up entries, including Mega Tyranitar. And there are at least two of those in this.
So much for Mega Evolution being caused by the bond between trainer and Pokemon... Any possible way to use this aspect to reconstruct it?
(Wow Nintendo, don't go and undo everything you fixed with Black and White...)
Edit: This might be something to look at for a reconstruction.
@OtomostheCrazy If you need a summary, most of the group went exploring the caves and have run into a horde of Zubats and Golbats. That's the main thing really, not much else has happened.