Wasn't unheard of back in the day, that you leaked things via PHP templates, like serializing and adding the whole user object including private details in a Twig template or whatever, it just happened the other way around kind of. This was before "fat frontend, thin backend" was the prevalent architecture, many built their "frontends" from templates with just sprinkles of JavaScript back then.
But there are more people trying to secure this framework and the underlying tools than there would be on some obscure framework or something the average company built themselves.
Also "pay a real provider", what does that mean? Are you again implying that the average company should be responsible for _more_ of their own security in their hosting stack, not less?
Most companies have _zero_ security engineers.. Using a vertically-integrated hosting company like Vercel (or other similar companies, perhaps with different tech stacks - this opinion has nothing to do with Next or Node) is very likely their best and most secure option based on what they are able to invest in that area.
PHP was so simple and easy to understand that anyone with a text editor and some cheap shared hosting could pick it up, but also low level enough that almost nothing was magically done for you. The result was many inexperienced developers making really basic mistakes while implementing essential features that we now take for granted.
Frameworks like Next.js take the complete opposite approach, they are insanely complex but hide that complexity behind layers and layers of magic, actively discouraging developers from looking behind the curtain, and the result is that even experienced developers end up shooting themselves in the foot by using the magical incantations wrong.
What’s worse is vercel corrupted the react devs and convinced them that RSC was a good idea. It’s not like react was strictly in good hands at Facebook but at least the team there were good shepherds and trying to foster the ecosystem.