> Next.js is the new PHP, but worse, since unlike PHP you don't really know what's server side and what's client side anymore. It's all just commingled and handled magically.

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.