There are many crowd-funded things that have turned out spectacularly bad in the past. So it's not even a case of just games, but any number and type of projects that can greatly disappoint. Either because they don't come out at all, or they come out but are different to what people imagined, were promised, etc. That's just the nature of crowd-funding, once we get down to the basics. Some projects have burned people before.
As for convincing someone as to whether something's worth it, without knowing a heck of a lot more about the individual, I think that turns into a very hard, very subjective topic. You know what you like... does CoE embody the same sort of things for you?
So all I can really offer, personally, is the same thing I'd say to anyone, in any crowd-funding situation out there. (1) Does the project interest you? (2) Do you want to buy-in to the idea - literally - deeper than someone just passing by and actually become part of the community that's putting its money where its mouth is? (3) Do you have spare cash that would otherwise be spent on a few cases of beer, some new clothes, or a weekend away, etc, that would otherwise be just as lost as if you did spend it on a project that went belly-up in a worst case scenario? If yes to all three things, backing at this stage of development and helping a game have a shot at being made is basically a no-brainer.
For someone who isn't sure about the game, or doesn't want to be involved at that deeper level, or really doesn't have spare cash lying around, I'd always advise caution. Hang out and see what happens with your interest level and/or cash reserves, and decide later.