I want to say those are bad examples but nonetheless valid. A better expample would be Javascript's strict-mode situation. In less civilized times, you could

I want to say those are bad examples but nonetheless valid. A better expample would be Javascript's strict-mode situation. In less civilized times, you could do all sorts of terrible shenanigans with javascript, and luckily for developers strict-mode gained support to the point where everyone naturally assumed you were talking about a strict environment. When ES6 came around, those 'sloppy' mode differences made implementing new features tough, so with adopting ES6, 'sloppy mode' was implicitly dropped. So yes, the web isn't by any means backwards compatible-- but definitely better at it than most ecosystems.