> The internet is responsible for around 5% of global carbon emissions.

Right, the internet (not necessarily the web)

> The solution however is fairly simple — use less data

Agreed.

> Fast, accessible websites usually produce less CO2

That's a drop in the bucket. If you look at what's _actually_ using data on the internet, it's streaming services (netflix, zoom, spotify). Fast, accessible websites have plenty of benefits, but if you want to actually reduce the amount of waste, far more effective solutions are things like lowering your video quality slightly (backgrounding futurama? Drop it to 480p.)