I think anyone is welcome to try this, but the core ethos of the web is backwards compatibility. To my unending irritation, even non-standard behaviors/APIs like WebUSB have become critical for sites to function.

The last time we actually dropped a feature, it was Flash, and that took a decade and there is still tons of effectively dead/permanently lost content because of it.

Creating a browser that only implements a subset of the standards is fine for very niche usecases but I don't expect it to ever overtake the major browsers. We'll see how Ladybird fares as it's compatibility increases.