The half-baked replay function in FSX is pretty much doable in an afternoon (which I did and released for free here [RELEASE] Flight Recorder - Free replay tool).
FSX replay function is bad considering the huge extensibility of the platform (even from FSX era). It was built with a very closed mind and lack of consideration for 3rd party aircraft, so although I also long for a replay function, I would rather wait for a proper design that actually work with 3rd party aircraft. A proper design, unfortunately, will never come if Asobo rushes a release before complex 3rd party aircraft.
Of course Asobo can also release a half-bake feature now and change it completely later, but for me it’s a waste of effort in development and support (and all the toxicity around here when anything doesn’t work as expected) for a mid-size studio.