Advantage/disadvantage
Bounded accuracy
Subclasses
Non-symetrical class design
Old school feel
Inspiration
Backgrounds
Magic items dissociated from math
Magic item Christmas tree eliminated
Bounded Accuracy making even low CR enemies like orcs still a danger at higher level
Magic powerful, yet doesn't trivialize the game
Simple to prepare and run compared to past editions. Much easier on the DM.
Meaningful backgrounds incorporated into the character creation process.
Simplicity of rule set allows for easy modification to personalize the game or characters without damaging the internal balance.
Not sure what you would call it, maybe the "Old School Feel" sentiment? I like how it reminds me of AD&D and 3.5, and just plays really well. Like it pulls the best from old editions, and adds a few new things into a neat package. Someone probably has a term for this already...
Oops. I read the first paragraph (that you were collecting suggestions) and then got distracted by my son, walked away, then came back and assumed I'd read it all. I'll edit when I know my one favourite...