There are also a lot of games out there that are just bad and difficult for the wrong time wasting reasons, and there is also a ton of selection compared to back then. Kids are probably showing rational behavior in picking the 'best' experiences. Old NES games and such were hard either to get more quarters out of you in an arcade and because they didn't have much space to program games, so they made them hard to increase the play time and 'satisfaction' feeling.
Also when I was a kid, early childhood I just couldn't really play the harder games, late childhood I could play the hard games. When they're just too hard you stop playing. Also different kids have different strengths and they will gravitate to games that play to their strengths. I have below the mean reaction times so I just did bad in reaction time platformers and eventually gravitated towards games that weren't hard because of reaction times, like RPGs, strategy games, installing linux on my computer and troubleshooting it and what not.
There are also new 'hard' games out there that demand a lot out of their players, and be careful if your kid gets obsessed about them. Like many esports games.