Making a habit of doing small puzzles like that can compound a lot over time. I am self taught and did not study algorithms in school, but I would consider myself stronger on the topic than most of my coworkers just from my learning to solve puzzles (and enjoying it). I am currently the senior / lead dev of my team.
I also love Advent of Code and look forwards to it all year.
I do both in languages that aren't what I primarily use at work.
Everyone including myself who does similar things of experimenting with different languages, do so with "real" (not sure what else to call it) programs on our machines for some purpose. Maybe recreate something else we did recently, or try it for that one specific use case we saw it potentially good for. Not doing random exercises on some online platform. I don't doubt some people find it satisfying, just interesting I don't find those people around me I guess.