rounser said:
Don't turn this into an edition wars thread. (What's wrong with breath weapons other than fire anyway?)
This so-called mechanics over flavor sin has always been part of the game from its very beginning and that is obvious, regardless of which edition you might prefer (by whatever standard we would be discussing at the moment).
As aptly put by another poster, slapping a coat of paint on a dragon is a perfect example of what your are decrying. The logical alternative would be to design several mythologically inspired different dragons that would (mostly) all breath fire, and that is how to get real flavor. Not exactly rocket science, but avoided in favor of mechanically inspired gimmicks.
In a universe with Gelatinous Cubes, Mind Flayers, Rust Monsters, Beholders, and Shriekers I do not find your list particularly troubling, even if I do not care for them myself. (Except for that stupid doggy that peels back its face. Cannot stand that one. But the must have been designed by someone's 8-year-old child...?)
You're kidding, right?

For every synergistic combination this makes possible, it makes a mockery of the flavour in countless others...nevermind suggesting the notion of a world full of randy trolls and dragons mating with every other random species in sight.
If abused, yes, it is painfully lame. It is not news that DMs need to exercise some editorial control.
But as a mechanics templates are beautifully flexible means of generating themed groups of creatures. Want to journey to an Unseelie influenced island? The DM can build ~1-2 Dark Fey templates, using existing templates as a guideline, and slap them on most of the critters in the MM in seconds. Not perfect, but it gets us 90% of the way there with almost no effort.