Web pages should be blazing fast on *25 year old* machines, modulo a little lag from more serious crypto.
Like, I should be able to build *1998 Mozilla* against a modern SSL stack on my Silicon Graphics O2, and browsing the web should be nearly as fast as it was using Netscape Navigator 4 on that system when it shipped.
The sole reason it’s not is the hubris of the people developing those web pages.