Frankly, I've just given up. It's just heaps upon heaps of utter trash. Every time something just slightly nice is made, it is quickly drowned out by the 1000s of clones are almost always much worse and full of ads and microtransactions.
This is not consistent with my experience. I suspect it's the overly broad nature that is wrong. Mobile games are usually much shorter and much simpler gameplay than desktop/console, which aboslutely are cheaper to make. If what you meant was "the same game on desktop and mobile is similar expense to make" then I agree, but you should specify those constraints as those are important qualifiers.
The numbers on Monument Valley are interesting: https://medium.com/@ustwogames/monument-valley-in-numbers-ye...
What accounts for that? Even discounting AAA desktop/console games, mobile games are generally expected to have less content and they're written in higher level languages.