Beyond the abuse and sex trafficking ties (or the right at the edge of the legal definition but certainly not entirely consensual), revenge porn, and such, the impacts of porn on humans have been exceedingly harmful. There's the whole "PIED" (porn induced erectile dysfunction) thing, where a boy or young man's brain has been so wired from porn that they can't function with an actual woman, you've got disturbing increases in physical damage to people (mostly young women) from boys trying what they've seen in porn, etc.
It's not harmless, on either end of the process, and as far as age gating, I'm not aware of any of the porn sites even trying to do anything until legally required. A 10 year old with a smartphone has no trouble finding things way over their head.
So, yeah. The experiment has been tried and found wanting. I'm perfectly fine with them trying to make it illegal, or at least "radically harder to access than it is currently," which is "zero roadblocks at all."
Society, and humans, were rather better off when you had to walk through the curtain into the back corner of the video store, or get something from the papered off magazine rack at a seedy gas station, than having it available, in total privacy, 24/7.