I have been given the sense that maintenance means things like routine repairs (new doorknob, broken light fixture, a stuck drain) routine preventative upkeep (winterizing, etc.)

The fact that you care enough to go in-depth about a routine PM task is a great example of your character and values.

Nothing to really feel bad about because it happens so much that it can be considered routine.

Start creating systems for things you do every day, like a checklist for your morning routine, because you’ll have to systemize your business to scale.

I don’t use a property manager  so that may make me biased but there are a few that raise eyebrows for me.  

If you're going the umbrella insurance route, make sure it will cover you for several things including just the routine slip and fall (like mold or earthquake).

What are some things that beginners are routinely failing at? 

Preventative maintenance is smart, but in my experience as an investor and property manager, the AC filters are really the only routine maintenance item you need "eyes on" for more than annually. 

I routinely find distressed, on-market properties on my local MLS here in Springfield Missouri. You can find great deals just by making enough low offers.

How quickly the coronavirus mocked our assumptions and challenged our simplest routines.