It seems like if what you’re showing is what you understand they find appealing and fun, then surely that’s what should be in the game. You give them that.
But instead, you give them something else that is unrelated to what they’ve seen on the ad? A gem matching candy crush clone they’ve seen a thousand times?
How is that model working? How is that holding up as a marketing technique???
Generally they’re not malware
Not malware, just ad revenue generators. Although I guess this depends on how widely you define “malware” since many of them are probably scraping, at a minimum, usage statistics while you play and possibly also device data and who knows what else.
You get 1-2 minutes of gameplay in between each ad and all of the “levels” are probably generated once by a program (rather than a human actually designing the level layout/challenges) to minimize startup costs. I’d be willing to bet that if you traced the ownership structures for the types of games the OP is talking about you’d find a handful of megacorps owning hundreds of them and just reusing assets and programming as well.
Then of course there’s the sinister preying on your psychology in subtle ways to keep you invested just enough to sit through the ad the play the next level.