People say they hate free-to-play and that they’d happily pay once for access like a normal game, but the stats say otherwise.
I wanted to replay Planescape: Torment, and I knew it had a mobile version. Oops, it's not compatible with modern Android. Situations like those teach me to stop bothering with mobile. Then there's the fact that if I want to play the game on a larger screen once I'm home, not only do I not get the desktop version of the game included with my purchase, but there's also no standard, easy way to sync my saves. Like someone else here in this thread, I stick to board game adaptations and things like Slay the Spire (which I've also thoroughly played on desktop).
People who use ‘mobile game’ as an insult are usually wilfully ignorant about the platform and just have an axe to grind.
The mobile games that bubble to the top and are the most played are often driven by some of the worst business models, so it's not surprising to me when the term becomes a pejorative, even if there are good mobile games out there.