Firefox

It's not even that Ublock/bloat is slowing things down, web sites are plagued by bad development and multi-standard requirements leading to tons of wasted processing time waiting for elements which eventually error out. I've analyzed performance on multiple websites, even big-name and high-traffic websites like Youtube and found that 60%+ of load time is just sitting there doing barely any processing while waiting for extra remote services to be contacted only to never load and finally fail allowing to page to go interactable. It's like having a beast of a computer but forgoing actual RAM in place for pagefile-as-ram; all other components could be amazing, but you're paying that performance tax no matter what.