I see, and I mostly agree. When creating your initial scope it's indeed important to make sure you have time to polish and stuff. But it's also vital to have at least one mechanic you know is fun in there. For an arcade game it's improving your skill and getting higher scores, and for an idle-esque/permanent upgrade style game it's seeing progression in possesion. When starting out your game it's important to constantly keep in mind one of those goals immediately to avoid having to hack it into your game later. If you then think of adding some optional feature before having the basis of what makes your genre fun, you can put it on a list for later or ignore it completely.
With 72 hours it's indeed easy to overlook certain things that in hindsight you would have thought about earlier in development. And I think the stuff that you did make was cooherent and executed really well.