Y'know, if not for the name recognition (and the fan expectations stemming from it), Cheetor & Rhinox work fine for what they are, which is essentially toy-only characters making a cameo appearance. Like, if you'd just search-and-replaced the movie Maximals with, I dunno, B'Boom, Sonar, Ramulus, and Jawbreaker, would people still be complaining, or would they just be thrilled that their obscure favourites actually got any screentime?
See, the thing about all of these movies is that Hasbro wants to sell as many toys as possible, but the writers and VFX people don't want too many characters, so we end up compromising with either multiple off-screen characters (as in the early Bay-based toylines), armies of cameos who don't really do anything for the plot, or multiple equally-inaccurate toys of the same character.