"modern web practices" may be more to blame than the browser. It's possible to make lean fast things running on browsers (within reason), but the culture is nobody gets fired for bloat. It's ubiquitous, same for mobile apps, server side, etc.

The browser is responsible for providing web developers with ever-increasing resources to eat up. It also defers way an increasing amount of much functionality to javascript (or at least allows javascript to reimplement that functionality) - e.g. there is no native support for DASH video so you are always beholden to whatever js the website uses (unless you want to use website-specific hacks).

There's no desktop standard. Desktop operating systems are either proprietary or niche. Any application you write needs to be ported again to each operating system separately.

The web is the closest thing there is to a ubiquitous operating system. And with the development around WASM, performance and efficiency is getting closer and closer to native. That's along with built-in security and sandboxing.

This is all around a good thing.