Essentially what you’re saying is “if you’re addicted, why not choose to not be addicted?” and… yeah…
Personally my biggest complaint is not necessarily screen time in itself, it’s that the tech giants are dedicated to maximising your (and your children’s) watch time by showing a stream of addictive slop.
It’s a shame, there’s good content for kids on YouTube but the algorithm always biased towards addictive crap. And they’re cornering the market to the extent that other operators producing good kid-friendly content (like the BBC in the UK) get sidelined.