You call hardly rule that the whole internet should be only for play. I'm marking exam papers at the moment. Over the internet. That couldn't be construed as play in any way shape or form.
That's fair, though I think
@Lanefan's point about the Internet being better off not monetised was more concerned with how the majority of the Internet is in the hands of a few conglomerates whose growth strategy relies on attention economy through ad revenue. Old Internet was much more of a sprinkling of small communities that were created for the sake of the thing discussed (and I'd say forums like ENWorld are a relic of that past), but now communities and people on Facebook, Twitter or Youtube care more about getting more attention so that either they or the platform that hosts them can earn money. This leads to a misalignment of goals because you might start doing things that you normally wouldn't just to attract more attention. You might start producing clickbait content if you're a D&D youtuber, for instance, or you might restrict certain kinds of (perfectly legal) speech because it's not advertiser-friendly. I think these kinds of considerations weighing heavier in the minds of communities and content creators is unhelpful for hobbies in the longer run.
As for
@Hussar's comment (sorry I can't quote it properly! It popped up while I was typing and I just wanted to address it in its larger point without going down into specifics), I definitely don't think that monetising your hobby is a moral failing in any way. Like I said, as individuals in a capitalistic society, we have to make a living somehow and if your hobby is marketable, it's only rational to do that (it might even be moral if your choices are monetising your hobby or working in an overtly harmful sector like an oil or tobacco company, for instance). I myself run a geek culture podcast and if we got some sponsorships offered, I'd accept them in a heartbeat (provided it was a company I was okay with ethically, of course).
As for gaming being commodified from the start, certain parts of it were, for sure! Production of rules and content as well as gaming aids, for one. But I think the commodification of the experience at the table itself is new. And I think it's understandable that the line we're crossing is met with some trepidation.
(Also, if it were down to me I'd say any and all hobbies should be completely decommodified and everyone should be able to live decently without needing to sell your labour for wages, but that's obviously not the society we live in. It should be helpful in showing the kind of ideal scenario I'm working from, though.)