Hey there, I'm definitely not an expert but I know where you're coming from. For all intents and purposes I started playing at age 59 so I know how difficult it is to learn new complex fine motor skills as an "older newbie", as you put it. If you're looking for something that's not formulaic then you'll want to play songs scored in notes or arpeggiated chords. Most newer beginner publications starts out teaching chords whereas older publications tend to start out with flat picking. Check out your local guitar shop for new printings of older beginner guitar books. Or, Amazon allows buyers to sample something like the first 10 pages of any book. Or, you can check the song catalog for "Acoustic" songs. They tend to contain sections of flat picking.

If you want something challenging, check out the intro to "Hotel California" in the song catalog (taught by Anders). It's about 16 bars composed almost entirely of flat-picked arpeggiated chords. It's a great "exercise" to play over and over, even at slower rates. I've played it at least 200 times and still haven't mastered it. But I'm getting better.

Nicolai