I cannot reply on behalf of concept game, but I can definitely give you some insights as to why the Spriter Extension has become a very important part of my workflow, beyond simply the cut-out animation:
* within fusion, you can use the Spriter unlimited 'trigger events' to eliminate pieces of redundant code: Most of my animation transition is done via the trigger and variables within the Spriter files, which I can set while creating new animations. Same with playing sound, or any other particular event which can occur during a given animation (change of character status, creation of hitboxes, creating visual effects, calling specific pieces of code as a call back, etc).
* the ability to have unlimited "action points" or even get at run times data about a specific piece of animation's position and angle (for example, position of the "head" sprite). This is extremely helpful when you want visual effects to be created during a specific animation.
* the ability to have animation Strings, integers and floats that you can define in the animation file, and then retrieve within fusion code to have specific behaviors during run time.
* the fact that you can in real time edit and reload the spriter file, tweak the animation and have that update taken into account without doing anything in Fusion directly
All of the above (and many more things which one could probably do to accommodate one's specific workflow) are extremely powerful tools as opposed to the native "active" objects Fusion offers. However for what you describe, and especially if active objects are already cemented into how you manage animated characters and object, what I mentioned above would probably not be of any help, as I don't think Spriter as an animation software is really as powerful and ergonomic as some of its competitors.
Also, I should point out that the extension still has a few major issues regarding performances and visual artifacts (which you can read about in the above comments). My biggest concerns are the loading times (which is extremely slow upon creation at run time compared to that of an Fusion active object) as well as the fact that animation does not seem to work properly outside of the camera view (which is a big issue for the aforementioned Even triggers, values if used to command some specific behaviors through the Fusion events).
I do wish these would be fixed and optimized by someone in the community who masters c++. But even with the drawbacks I mentioned, I could not go back to using active objects anymore for main characters, enemies, etc.
I hope this helps