browsers are quite fast nowadays.

they appear to be bloated mainly because of two reasons:

1) companies pulling in all sort of un-optimized content and making requests to a huge amount of external services, effectively slowing down the render of pages

2) a lot of developers developing stuff that should really be native code in html+js+css, which doesn't always perform that well and tends to slow down the whole browser. it really suffices one badly-coded app (not using well asynchronicity and/or wasting memory) to make the whole browser appear slow.