About 20 years or more ago it was not uncommon for a “webmaster” to be a jack-of-all-trades. Things have changed a lot since then.
Technology has advanced so that now being an “expert” in any role is not an easy task (grossly understated). It is now more common to “specialize”.
a “system administrator” would be in charge of configuring and maintaining the server.
a “programmer” would work with code.
a “community manager” would have the responsibility of forum content and guidelines.
Even though being knowledgeable of other areas is a good thing, it is not necessarily true that any one person will have more than a cursory knowledge (if any at all) of areas outside of their area.
There are times when I think having a recognized certified / licensed thing would be a good thing that would help promote web development as a true profession.
Having a degree from an educational institution doesn’t hurt, but what most consider as web dev (let alone specifically Discourse) “credentials” are experience and real-life examples.
As admirable as it is that you are interested in learning it all, is there any one thing you’re most interested in?