I recently bought a cheap&small office laptop with intention of taking it with me and completing assignments in public places. Problem is, it chokes up and dies when running more than eight tabs on firefox. I also tried k-meleon, it has great performance but the UI is ancient and many websites that I need dont support it.
I’ll echo other comments in that the modern web is a mess and it’s hard to escape the bloat unless you’re using a text browser.
But what could help is Firefox with add-ons like uBlock Origin and Noscript. The former can massively lighten the load on ad-heavy sites, and Noscript will let you block the bloat of JavaScript while allowing specific bits if the site breaks with all of the blocks.
NoScript is redundant if you use uBlock Origin, as it allows to toggle any scripts and domains running within webpage.