It's worse than that, even, since those modeling programs would be more akin to something like Audition or ProTools on the sound side.
Licensing a plug-in sound engine is more like getting a plug-in graphics engine. The way the final product looks depends entirely on the assets you put through it, and the aesthetic direction taken - not to mention the skill of the director and the artists. However, the expression possible with that engine is partially determined by the way it works at a low and, more immediately, at a high level, that you can probably learn to recognise "signatures" for that piece of middle-ware. For instance, I could probably recognise a Lithtech engine from an idTech 2 engine from an original Unreal engine powered game fairly quickly. I'm sure the kids today can tell a CryEngine game from an Unreal one, or Frostbite etc. too (although, the homogeneity of post-processing in particular, in terms of aesthetic targets and the hardware / APIs, means that's probably harder).
Couple that with the way a given package exposes those "functions" that developers use for "expression", in terms of the built-in structure of the "engine", and you find that the choice of "plug-in" determines the way that the game systems as a whole work and interact (because you have to build an interface between that engine and your other systems).
So switching to a different engine can be a bit of a chore, even if it's a comprehensive one ("all" "base" systems: audio, graphics, logic etc.) like Unreal or CryEngine. It's great for developers just wanting to push some games out, and you can work around the imposed functionality of a given (combination) of engines, but if you really want to do exactly what you want, then you have to go bespoke.