Very interesting, in summary...
All the problems of handling emails!
More code
More platforms
Less standardized
Not integrated with password managers or browsers
More steps
I found it annoying to use myself:
1. Go to arp242.goatcounter.com
2. Enter my email.
3. Go to FastMail.
4. Wait 10 seconds to 5 minutes for the email to arrive.
5. Click the link, opening a new logged-in goatcounter tab.
6. Close the old goatcounter tab where I filled in my email and FastMail tab.
Whereas with password auth it’s:
1. Go to arp242.goatcounter.com
2. Enter my email and password.