RE: Action Masters
Unlike
Ultimetal Optimus Prime, Action Masters weren't just non-convertible merchandise or a sub line of toys - they were part of the "mainstream" line of Transformers and they comprised a reasonably significant part of the toyline at the time. This
Ultimetal Optimus Prime is a piece of Transformers merchandise, it's not part of the action figure line proper. Transformation is a significant part of the appeal of the Transformers franchise - the 'puzzle play' is a core part of the Transformers line's play pattern. The bread and butter if you will. I can understand that there will be 'peripheral' toys and items of merchandise that don't transform - we've had that since the 1980s (e.g. voice changer Ultra Magnus etc.), but I think that action figures that are part of the "main" action figure line ought to be able to transform. ROTF Combiner Class Devastator was another more recent example of how a toy that didn't "really" transform (i.e had no individual robot modes) wasn't received well by the market, as evidenced by it's incredible shelfwarming.
As Cat said, this is not a toy. It's a piece of merchandise. It's a very expensive piece of merchandise, no doubt... but that's what it is.

And as he said, if we want something to play with, that's what proper action figures are for, like MP10. Action Masters sucked because they existed
in lieu of proper transforming action figures.
Ultimetal OP is personally not my thing (neither are busts or statues), but I don't begrudge it either. It's not a toy, and it's not trying to be a toy... unlike Action Masters who were very much marketed as being part of the core action figure line.