To some extent hiring is always aspirational: a reason a company wants to add more people is to get better at skills it thinks it lacks.

This applies particularly to aspirational projects that a company "wants" to start. It hits a chicken-and-egg problem of that it needs to hire skills for that project, but can't start on that project until it hires those skills, many people don't want to be hired unless that project is already off the ground, and in the meantime existing projects still need to be maintained...

Certainly it would have been better for the interviewers to more accurately describe how aspirational their goals and not imply that things were more off the ground than they were. It's a bad way to start a relationship by selling goals as reality. It's also a sadly common way for companies to start relationships.

If you want to try to contribute change, figure out what the roadblocks are to that aspirational project. See if you can find ways to apply your skills to the aspirational project. Sometimes companies forget the bootstrap step in that chicken/egg problem and forget to check if they've added enough resources to start pitching into the new work. Goals continue to be delayed because the company is uncertain and being deliberately conservative about if it has the resources it needs to meet its goals.

Sometimes an aspirational project is looking for a leader to step up, someone with enough passion about the future to get the work started and get prototypes out the door. There's a possibility that can be you, if want to apply for that pressure/responsibility. There's a possibility that in hiring you your managers hope it might be you.

As much as anything, there's a chance here to introspect and figure out if it can be you. Figure out if you can make that pressure/responsibility work for you, if you can make the work/life balance you need, if you can find a way to balance work's existing responsibilities on you (help maintain current systems) with potential new responsibilities (help lead new project). In some companies you might be very well rewarded if you can strike that balance, if you can lead the company onward to meet its goals while helping it survive with its existing needs. It's up to you to assess if the rewards are worth the risks. Your company might be one of the very many that aren't that loyal to its employees and you would be better off elsewhere, but that's something you probably need to judge for yourself.

I guess I'm rambling, but there are ways to make your situation work, if you are looking for them. It's as much on you to discover if you have that capability as it is for the company to solve its own paths to its goals. Starting that conversation with a lie of omission might be an indication of bad faith and disloyalty from the company immediately off the bat... or it might be a sign from the company that it really wants someone/anyone, and that someone could be you, to step up to bat and try to knock something/anything over the plate. It's rare that a company wants a new hire to strike out. Maybe if you can hit a home run you might be rewarded for it, and it might be worth swinging for the fences. Have the conversations you need to figure out if it's worth the pain of swinging for the fences versus playing it safe and bunting until you get the next job offer.