Windows NT on 600MHz machine opens apps instantly. What happened?

A lot of people are bringing up Wirth's law or other things, but I want to get more specific.

Has anyone else noticed how bad sign-on redirect flows have gotten in the past ~5 years?

It used to be you clicked sign in, and then you were redirected to a login page. Now I typically see my browser go through 4+ redirects, stuck at a white screen for 10-60 seconds.

I'm a systems C++ developer and I know nothing about webdev. Can someone _please_ fill me in on what's going on here and how every single website has this new slowness?

A lot of sites now don't even a "sign in" now. You only have a large "sign up" button, which you have to click, and then in very small text at the bottom of the sign up screen find the link for "already have an account?"