True, although even without ads nor a bloated stack, you start with network latency, code running in a VM that has to use hardware with terrible embedded gpu, accessibility requirements, seo, and so the obligation to use the dom api, the latter not being accessible throught a compiled language.

Also, the website teams is usually smaller, and have a 10th of the time to ship.

But it doesn't excuse everything, for sure. Most websites should be fast given how little they do.