I've got a great example of what you described (not to be confused with good) There's a mobile game called "Hooked inc." I installed it on a whim while looking for something to similar to an old PC game I used to play. I played until things slowed down and to really progress in a timely manner you needed to spend the paid currency, but you can acquire it slowly by watching ads. So I did for a bit. Had the idea of an auto clicker macro so it could accumulate while I sleep, put an android emu on my laptop and did that until I discovered that the creator hadn't anticipated keyboard access and had left in some shortcuts (presumably for testing). One button , i, u, or l maybe, gave you a skill point to spend, another gave a spin of the wheel without watching any ads. I maxed out the skill points and set a macro to constantly spin the wheel. Bought all the passive bonus characters and leveled them up, got tons of the rare items and leveled them. Made it significantly farther. Did a little math to see how long it would take to finish grinding out passive bonus levels and experience to get further. It would take days or weeks of spinning. Made me really feel bad for those watching ads thinking it'll help them make some progress. Uninstalled the game a couple years, reinstalled to see if my "progress" has been wiped. Nope, but with all of the additions it felt rather insignificant. They'd added more grindy ad mechanics.

Sorry for the novel, Tldr for these games you can watch ads nonstop for weeks and have nothing to show for it. Better off uninstalling.