I've actually played a good bit of downloadable games, and like you said, they tend to be low on ratings, however I find downloadable games to be generally more enjoyable, as they tend to be longer and feel better.
I've seen a lot of people in this jam post their Unreal games, and a VERY big problem is that these games are absolutely massive (normally over 300mb) regardless of how much content is in the game.
Most of these giant file sizes come from the unnecessary plugins and extra stuff that Unreal packages into your game, and it's definitely worth it to find all of these and clean them up.
Default Unreal settings also don't compress your assets enough, so you might want to get some asset cleaner to help you with that.
Of course, people can still download your game regardless of the file size, but taking upwards of 5 minutes in downloading just to be able to play your game(mainly for people with worse internet) leaves a bad taste in people's mouth.
This is by far the main problem with downloadable games, and very important to keep in mind for future game jams.
Edit: This may not be just a problem in Unreal games and more obvious in all 3D games in general. Cutting down file sizes is still possible though.