As someone who's been using an old laptop for many years, I can tell you it becomes more and more challenging. With just 2 CPU cores, even Firefox (with it's threads showing as "Isolate+" in
top) can easily consume both cores. I can only imagine it gets much slower a few years in the future. Websites become more demanding.
This brings me back to my earlier conclusion:
Privacy is cumbersome.
It's not the websites that are becoming more demanding, it's the tools (browsers) we use to navigate the internet.
Nowadays, having Chrome (for example) open on the simplest websites we can visit, and it takes up +20 processes and almost 1GB of RAM, not to mention the processor usage. It's true that due to the increase in internet connectivity and improvements in server hardware, many websites have stopped worrying about the space/resources they consume. Even so, I think it's the browsers themselves that are demanding more than what is really necessary.
Either way, I agree that increasing privacy levels is increasingly more work and increasingly complicated.