We can blame those that make the web pages but alas, it is the end users' systems that suffer, and in turn, that makes it also the browser and perhaps OS maker to step in.
That is funny. I had rMBP 13 2012 with 8GB RAM/128gb ssd for 8 years, there were only few times when i saw a beachball or had the system lagging. Overall when lagging, i was tracking the activity monitor, so 99% of the time I just had CPU (dual core only) maxed out at 100% use which obviously created slowdowns if ever. My RAM was always sitting between 5 to 7 GB. It has
Sierra on it. My RAM pressure is green.
Currently, with M1 Air 8GB/512GB on Monterey, 8GB is nothing and I always in a yellow/red RAM pressure zone. My 8 core M1 CPU barely struggles while always being used only for 5-25% of load, so clearly my bottleneck is RAM and MacOS. Funnily enough, first 2 releases of BigSur were totally fine with me and then things went downhill.
Artisright mentioned one things that awaits us: Studio introduced 20 core CPUs with 128GB of RAM - there is so much less incentives to hone your code and make less power hungry software. Apple with its' buggy MacOS is not helping either - I restart once a week now, used to do once a year.
PS. My habits haven't changed at all since i am conservative and only visiting the websites that i always used. My work habits also the same since using above 2 laptops I was doing the same job on my laptops for the last 3 years.