Anil Dash has a long essay on the state of the open web and not all of it rings true for me, but buried in the opening is a wonderful definition of what the open web actually is:

The open web is something extraordinary: anybody can use whatever tools they have, to create content following publicly documented specifications, published using completely free and open platforms, and then share that work with anyone, anywhere in the world, without asking for permission from anyone. Think about how radical that is.

It does feel like if the web got invented in 2026, it would not have been left as an open technology for long (see also AI and how much open source models are lagging).