Proprietary food.. that you can only buy from a single company are all doomed? Might I offer an example that, under some definitions, has not failed despite that strategy. The McRib.

I was going to offer the twinkie but I guess hostess declared bankruptcy, so maybe you're right.

It's not an unreasonable statement though that for the concept to work it has to "jellybean" though: many manufacturers, many variations, same basic product, ubiquitous availability.

Where it sits as a "premium" good doesn't really work as a value proposition.