I've given it some time and I still feel like my main issue with this Mega Malamar teaser is that the Mega Evolution aspect was essentially irrelevant to the plot. The exact same incidents in the videos could have been caused by base Malamar. In fact, the whole campaign was just about shoving base Malamar's design everywhere, because Malamar hypnotizing people is already an established aspect to be in on the joke about. But there's no mystery beyond that and so the punchline is just revealing how Mega Malamar looks different while it doesn't actually do anything new*.
This isn't even against Malamar itself, it would be a fine teaser for Malamar alone, but it doesn't really show the point of its mega evolution to me.
Compared to the past two teasers, I think they made a more unique showing of how mega evolution would affect their design changes/stat boosts and the bond between trainer and pokemon.
Victreebel's teaser involves a trainer being responsible for it by training in an isolated location because it's so dangerous with how it can barely keep its own poison contained as the video shows. This demonstrates how Mega Victreebel's design drastically changes how it physically moves and exists, and it even detransforms at the end to highlight it. Mega Victreebel does things that Victreebel can't do.
Hawlucha's teaser is all about training together with a trainer to win battles, and directly shows the difference between base Hawlucha and Mega Hawlucha before and after, using it as a comeback power boost against Machamp that lets it shrug off the same attack that downed it before to pull out the win. Mega Hawlucha does something that Hawlucha can't do even if the design change isn't as drastic.
Malamar's teaser is about it hypnotizing people and probably even its own trainer. So much for the power of bonds and trust. I don't know what Mega Malamar adds that Malamar couldn't do before other than being told it's more powerful by a biased source. The news broadcasters not knowing Mega Malamar exists makes the public just seem ignorant to boot.
*I did also find this description of its animation which I thought was just there to be weird, but if it's a self-hypnosis aspect like Psych Up I guess that is something new that Mega Malamar does. So I will give Mega Malamar this one thing if nothing else, it can actually affect the brain with stimulants. Better hope it doesn't get a concussion though.
https://legends.pokemon.com/en-us/news/mega-malamar
"It can stick its tentacles into its head and stimulate its brain for a rapid boost of psychic power."