I'd say the majority of games on itch disappear into the void very soon after being put on the platform and only really exceptional ones stick it out for a while, so most 'game jam' developers don't get any kind of prolonged traction here. That said a game jam can be used, as you implied, to develop some new skills, but also as a gauge for how successful a certain type of game or mechanic could be. I've done 7 of these things now and definitely detect some trends on what people enjoy and what they dont etc so its good in that regard. But I agree, if this doesnt shoot the lights out in terms of responses and overall scores etc take the lessons and move to the next project. For the swimming in this game maybe it would make more sense for the lines that you are swimming in to represent current that carries the player and you have to manoeuvre through the fast-moving water, while leaving the current actually makes you swim very slowly, opening you up to the risk of being eaten by the sea monsters. Thats probably quite a satisfying way to go if you have the energy for it after the jam.