Whoa, I did not expect to see Fathom show up on Hacker News. It's very early but our plan is indeed to go down a similar road as Matomo, albeit more opinionated. Hopefully resulting in a simpler product in the long run.
I feel it's important to point out out that with Fathom, no personal information is tracked (or stored), at all. Only daily and hourly aggregates are stored on the server.
And yes, the demo should not require you to enter credentials. The simple reason is that I haven't gotten to polishing that experience just yet. Sorry.