Good questions!

But problem is, all my email address would be @mydomainname.com instead of @protonmail which millions of people use. Isn’t that just linking all your account together.

I mean, yeah. You can’t setup sockpuppets on the same service. It’ll be obvious it’s the same person. And if someone is tracking you across services, it’ll be way easier to find you. This is a con.

I would recommend not picking a domain with your real name, like smith.com or john.com. Even though it does seem popular to have me@johnsmith.com. It won’t solve the issue you noticed, but it’ll mitigate it a tiny bit.

its hard to even pick a name that sound good

Also, true. Ideally, you pick a common word with normal spelling that doesn’t have a homophone that’s not embarrassing to say to random people on the street. It would be awkward to be applying to a job or a loan and have to say your email is “john@piggy.park”. Also, you will have to speak your email over the phone at some point, the shorter and easier it is the better.

I would also recommend picking a domain with either .com or .net TLDs. Some companies blanket destroy your email if it comes from some weird TLD like “.party” or “.xyz”. Omg, specifically, .xyz I think has been linked to tons of spam. Bigger companies will handle this more gracefully (put it in spam). But smaller companies, like my local garbage company run by normies, will just not deliver the email. (And debugging why emails don’t get received is really hard and annoying.)

Unfortunately, a lot of people squat domains, so finding a short, simple, easy domain is really hard. I’m curious what other people do. Maybe other people just have me@reallylongdomainthaticanactuallyget.com? Or maybe other people have had better experience with john@mail.club? Or maybe some people don’t care that their domain is john@boss.baby?

Ultimately though, having email independence is valuable enough for some folks to be OK with the downsides.