A little OT, and I'm not sure if iOS has this ability, but I found that while I'm traveling, if I enable Data Saver on my (Android) phone, I can easily go a couple weeks using under 500MB of cellular data. (I also hop onto public wifi whenever it's available, so being in a place with lots of that is helpful.)

My partner, who has an iPhone, and couldn't find an option like that (maybe it exists; I don't think she tried very hard to find it), blew through her 5GB of free high-speed roaming data (T-Mobile; after that you get 256kbps, essentially unusable) in 5 or 6 days on that same trip.

It turns out there's so much crap going on the background, and it's all so unnecessary for the general user experience. And I bet it saves battery too. Anything that uses Google's push notifications system still works fine and gets timely notifications, as IIRC that connection is exempt from the data-saving feature.

I've thought about leaving Data Saver on all the time, even when on my home cellular network. Should probably try it and see how it goes.

But overall, yes, it would be great if website designers didn't design as if everyone is on an unmetered gigabit link with 5ms latency...