How do Storyline beginners overcomplicate course building?

From some of my observations, 

1. As you mentioned, too many pointless animations.
2. Too many triggers. Often for what they want to accomplish, far fewer would do.
3. Related to that (although potentially advanced), shunning very simple JavaScript solutions that would eliminate tangles of project variables and triggers. I understand the desire to keep your project clean but some actions, while possible, are just orders of magnitude more complicated without it.
4. Creating overly complicated states. They quickly become very difficult to edit and troubleshoot. 
5. Not establishing and following a logical and consistent approach to organizing objects on your timelines. The same could be said about naming objects, but I am extremely guilty in regard to naming conventions.
6. Placing too many slide objects on a single slide or layer. Not sure if things still bog down as before, but trying to fight it rather than just hiding extraneous objects during editing was always a losing battle.
7. Developing projects without regard to the resolution of media objects. I tend toward larger media, but sometimes you'll find 4K or even 8k images stuck inside someone's project.
8. Failure to plan for accessibility before and during the design/development phase. The accessibility checkers are helpful, but after-the-fact compliance updates quickly become a nightmare.
9. More of a fundamental issue, but overreliance on templates. They simplify design but unless you eventually take the time to understand how to accomplish the task on your own, they can introduce unexpected problems and hinder skill development.