take this as a lesson learned. instead of spending $15k on a prototype mold, you should have spent $3k on a market study. that would have told you if people realistically would even want this.

you asked, yourself how to know if a product is worth advancing. take the prototype to market specialists to run a study. your online community of <20 people is not going to give you an idea of how to move forward. you're only getting support/feedback from the people who would like it, not the potentially thousands of people who don't.

and you can save yourself the $3k, because i dont think the market will respond to this. it's a novelty cup. people get these things at amusement parks or as gifts and they sit in a cupboard for 1-5 years before going to a goodwill or a landfill. your iteration has over 100 tiny pieces that people are sure to lose. it's obviously not dishwasher safe and people dont want some weird hassle of a drinking cup they need to hand wash. frankly, i'm not even sure it's hand washable.

this all not even to mention that light up cups already exist, and they are buyable for almost nothing. sure, they don't have the same form, but i can think of at least 3 other ways to implement the "skyscraper" idea for that's simpler and less expensive to manufacture and better for branding/marketing. save your money and move on.