If anything there are more young people online now since the internet is more commonplace and easier to get to. No longer do you have to be seated at a bulky big box four figured-cost computer hardwired to everything and using up the only phone line in the house for dollars a minute with a lot of technical configuration as an entry barrier. We beam the internet to our 4 year old's wireless $50 tablets so they can watch YouTube and leave us alone on car rides.
most of those COPPA things were more to protect the website and the service than the child, so nobody could just litigate that you were providing harmful and evil things to the youthful and get'cher ass FBI'd. Most internet-pioneer kids just learned to lie, and if the lie was ever found out then technically the website/chatroom/whatever provider wasn't liable since they followed the rules and did what they could to keep kids out. Unpopular as he may be these days, Moot is a perfect example, since he started 4Chan and made it an "18 and older only" community and banned anyone who let slip they were minors, all while he himself was only 14.
Whether or not the internet is better without the larger amount of people is arguable - it certainly was less gentrified, and the sense of community was stronger, but communities and culture always thrive better when it isn't a gated "cool kids club" kinda thing. Take for another example, this place, The Kiwi Farms. PVCC could be considered the progenitor of Kiwi Farms, since the CWCki Forums was a public offshoot for PVCC since PVCC was super gated, clique as all fuck, and from all reports (I wasn't there tbh) ultimately stupid and like, 10 guys sniffing their own farts, while casually drip feeding "cocks" or little stories of Chris Chan to the plebs of the CWCki Forums. Under new management though, CWCki made like the dirty red commies, seized the means of production, and left the bourgeois to rot in their tower. People brought new cows to talk about to CWCki Forums, more cows brought in more people than the narrow attention Chris Chan would attract, CWCki Forums blossomed and prospered while PVCC ultimately became irrelevant, and with a rebranding we became the Kiwi Farms. Say what you will about all the problems extra traffic and attention we get here bring, but you literally wouldn't be having this discussion if more people didn't come here.
I think children being introduced to the internet and having it integrated into their daily lives at a younger age is making their lives worse. from what I've personally seen, as well as testimonials/articles/etc., we essentially have "e-parenting" now, where you have parents that are becoming more dependent on the internet and devices to parent their children. this is particularly bad because, in lieu of discipline or behavioral correction, they divert the child's attention to something that is mindlessly stimulating, so there is no praise or scorn allowed to register. one of my friend's children seems impaired and I believe it is because they were heavily subject to e-parenting; the kid only plays Overwatch and, when not playing Overwatch, will ask about playing it and seemingly only wants to play Overwatch. their attention span is so short, it will ask in a few minutes if initially denied.
I think it's a no-brainer that this has huge negative impacts on the lives of these children, and that negativity will carry over into their adolescent and adult lives, and their collective negativity and reliance on the internet will ultimately affect the internet in the same way.
That's just how children are. Back in the 80s kids were hooked on Star Wars and arcade machines and just as narrow focused about those subjects as kids are these days about Youtube and Fortnite. Ask any parent of a toddler and they'll tell you how many times they've listened to "Baby Shark" on youtube. Ask the grandparents and they'll tell you how many times when they were parents their young ones burned through VHS tapes of Disney movies and Muppet show reruns. Its the same behavior, that's just how kids are. What really needs to happen is a change in how parents raise their kids. They can't rely on old tactics that worked for their parents and their parents before since the world is a different place now. Our parents had the misfortune of being on the front lines of this brave new connected world, and in many ways fucked up because they didn't wholly grasp the pitfalls, so we got a bunch of people in their 30s now that let their infants starve in their cribs because they didn't know how to manage being an adult and playing World of Warcraft in the right amounts. Hopefully this generation will have learned from watching some of their peers failures and not fuck up when its their turn, but it really just comes down to being a parent and not a friend to your spawn and providing ample stimuli options instead of always relying on the easiest and laziest stimuli, like unsupervised online games and shit.