I used Unreal and made my game in about a day so it's super simple but at least has a working loop (https://itch.io/jam/gamedevtv-jam-2025/rate/3586441). After last year's experience where I learned what you pointed out (for game jams people just want to play in a browser, fast iteration times matter), this year I implemented in BluePrints and focused a lot more on the fundamentals so whatever the outcome I've learned something new. Blueprints really helped with quickly prototyping stuff and the wide variety and huge amount of assets and ready-made samples available for UE helped building and learning although implementing it into one's own projects is still a lot of work. I'd consider jams more of an opportunity to learn and try new things in that sense although clearly it's possible to create amazing things too once you get a good handle on scope, tooling and dev process.