Earlier quoted context omitted.
If your main concern is the sheer number of username/unique password combos, pick a good password manager that works well across the devices you use. I’ve literally stopped caring about this aspect of my family’s online life thanks to 1Password. That iOS 12 added OS level integration for the service was the icing on the cake for me.
Using a password manager (which I do) is a valid coping mechanism, but does not fix the root concern: for 90% of these cases, one shouldn't even need an account. I don't want personalization. I don't want some new identity to manage. I don't want a relationship with your service. I just want to browse the goddamned web! How did we get to this point where in order to use the Internet you have to sign up for all these…
We stopped using sites built by amateurs in their spare time and demanded "beautiful user experiences" that we didn't pay anything for. That costs money, so people who wanted to solve that "pain" looked for business models that meant they could deliver what people want without charging directly. Hence we have an Internet driven by advertising and privacy violation.