Use your own domain to sign up for a paid email service, provided by a company that focuses on email. I use Fastmail, but there are many other options.

Set up forwarding in Gmail to your new address.

Then, whenever you log in to a website or app with your Gmail, take a moment to change it to your new address. In a few weeks, most of your important accounts will be covered. In a few months, almost everything you still actively use will be done.

I did this ~5 years ago and the only thing that still arrives at my Gmail is spam.

Same here but ~8 years.

You can mitigate/speed the process using your password manager too.

I still use a filter in my email so that if something comes in under my Gmail, it gets a special tag that I can filter on and treat those as a todo list. Rarely happens beyond the occasional Google Meet connection.

For quite some time (approx 8 years) I've used an email forwarding (Blur, but any works) to avoid spam.

This looks like perfect case for change of email, since lot of these accounts can be moved out from Gmail by changing the address that email is forwarded too.

Looks like all this hassle with generating a new email for each service pays for the second time (by ease of changing the main mail), in addition to spam and privacy protection.

Solid advice, but I want to double, watch out for things you only log into once a year.

Making a new local account on your machine is a good first step.