Right but other websites load bloat in the sense that it's all trackers, ads and other useless crap that doesn't add anything to the UX. Gmail on the other hand

Right but other websites load bloat in the sense that it's all trackers, ads and other useless crap that doesn't add anything to the UX. Gmail on the other hand all, if not most, of what is being downloaded is to have the rich UI that it gives. It's mostly not ads, and likely only GA or whatever they use internally as a tracker. I doubt those add up to more than a couple of MB. Other websites use many different third parties. I've seen some sites use over 10 different analytics tools on top of other other ad networks.