What are you talking about? Heroes and H2 had THE same creatures, They didn't copy-paste them because the end result would be out of place, but they did repaint them almost the same way. If they were using 3D models, they would possibly reuse some of them, as they appear alike. Take the wolf for example or the druid.
If they chose to copy-paste the creatures, they would have to go with the same resolution, same quality of graphics, same framerate, same art style, same detail depth, same colouring scheme. That would make the game feel like an expansion rather than a new game and it would actually be a restriction for the developers. Choosing to repaint the creatures was a choice that HELPED them.
You're comparing this to reusing tha same skeleton for the lamasu. This is neither here nor there. It makes sense to use the same skeleton for a creature you are reintroducing, since the level of detail, colouring, art style, etc can now change simply by changing the model parameters and its skin. You want to present a new concept for the creature? That's fine. You want to simply reuse the model and change its appearance only slightly? That's fine by me.
What your complain alludes to, as I see it, is the supposed fact that the developers are spending less time and effort to create H7 than, say, NWC did while developing H3. But that's completely wrong. H3 was much less of a bother for NWC, since most of the code, gameplay elements and game mechanics where transferred directly from H2. Therefore, if you're complaining that your "top dollar" should be paying for "top work", then your complaint is misguided; the H7 developers bother much more than the H3 developers ever did.