For me, it's been learning that software isn't king or the be-all-end-all of gamedev. I work as a programmer in my day-job and make games on my own for fun in my free time. This is the first time I've actually been actively in the community during a game jam, and it was eye-opening seeing all the artists, animators and musicians in the discord, as well as programmers like myself. This is also the first jam where I really put a lot of effort into the art and music and general presentation, and having to juggle that alongside designing, programming, playtesting, etc, was exhausting and left me with a big appreciation for the craft that goes into game development besides just the code.
I've also been getting more into board games lately, so that planted the seed of great game designs and systems existing outside the medium of software, and this just hammered it home.