I think it would be interesting to do some analysis on this, I don't think the author really had enough data to do it properly though.
Burger King had it easy. They let McDonalds do all the hard work of figuring out where to put restaurants, and Burger King just put theirs across the street.
Taglines, being the most heavily compressed medium possible for a startup to convey themselves, are simply that much more prone to positioning-speak. There is exactly zero room for customer education, all you can do is position.
Personally I think the way forward is to de-emphasize taglines, and move towards short blurbs. The startup space is entirely too crowded for USPs to easily conveyed in a single statement. But everyone expects you to be able to anyway.
Writing a concise description of a service that gets its use across is difficult. Comparing it to something else is natural. So let's see some improved ones.
But metaphor is unavoidable in modern parlance. Case in point? I invoked metaphor within the first sentence of this comment, totally unintentionally. DigitalSea's comment talks about this without actually calling out metaphor, but that's what it is. Lakoff, Johnson, and Frye talk extensively about metaphor--it allows us "to experience one thing in terms of another." Sure, when you smash too many concepts together, metaphor can lose it's expressiveness--but you can say the same thing about code (what happens when you have too many layers of indirection?).
The criticism should not be placed broadly on metaphor, but on poor use of it. "instagram for fashion" implies a bevy of ideas and is communicative--‘lego for data product makers’ is not.
I don't mind the cliche-ish descriptions as long as they are accurate.