There are ways out of this. The first is to find one or more partners who have the necessary skills to develop the prototype with him, in return for equity. Not willing to give up equity? Then too bad? Can't convince devs that your idea is not that great/unique/compelling (because we've ALL heard variants of this "my idea is SO great - all you have to do is code it and we'll be rich" bullsh*t)? Again, too bad.
The real "way out of this" is to realize that, since he doesn't have the necessary skills, he either has to acquire them or give up. Not willing to take the years necessary to acquire them? Like the old saying goes, "The will to succeed isn't as important as the will to plan to succeed." Not having a plan that takes the obvious potential obstacles such as the ones you cited into account is a pretty good indicator that you're not the one to invest in. After all, ultimately, people invest in people, not products. The product won't complete itself. You can't hold an incomplete product accountable. You hold the people behind it accountable.
Not only that, but having a dev (team) lined up when you run your KickStarter is a pretty good sign that you're serious about this--though honestly I'd be more inclined to go with a project where the dev(s) are taking at least part of their cut in equity, because that means the dev team actually has motivation to hold up their end. Some amount of wages may be necessary, but equity provides some motivation to release a product good enough to keep selling once people see the end product: This protects me as a backer, and honestly I'd feel more confident about the results if the dev(s), who should know a lot more than I do about the project, feel confident enough to be wanting equity. Particularly with a known good dev team, I'd expect them to not be likely to do that unless they feel sales stand a reasonable chance of being good.
A prototype of some sort is a good way to show that you really do believe in the product you're pitching me, which actually makes a difference. If you don't believe in it well enough to put in the work to show me even a very loose prototype, why should I believe in you enough to give you money? More importantly, why should I give it to you when there's other, equally-interesting projects that have put the effort into their pitches that you didn't?
If you're an established group, knocking out even a quickie prototype may actually be relatively easy--and it helps you narrow down what you actually are going to do once you've got the money. Are you going to make an all-new engine for your video game? Do you actually need to, and even if you really do, can you get a prototype going with an existing engine? (Slap on disclaimers saying that this is a pre-alpha version and significant changes will definitely happen.) This would probably give at least some sense of what sort of budget you may need to look at...
If you've already got a rep for delivering, you may not need to give anything more than "We have the basics pinned down," but you absolutely need the rep for delivering and it certainly would be wise to keep people informed about if there are delays. Even better is having a rep for timely and informative updates as well as one for delivering--not necessarily regular ones, since "We're working on it!" daily is less useful than even a long quarterly report whose tl;dr is "We have reached these milestones, here's some of what we've got to show you now, we expect to be reaching these other milestones soon." (Better would be a report on those milestones being hit as they're hit, as well as a notice when snags are hit and overcome, but still, infrequent informative updates are better than frequent uninformative ones.)