I've never flown X plane but I have flown plenty of other sims with compelling flight models.  Remember the old "Flight Unlimited"?  That flight model was just fine.  LOMAC has a good flight model.  The old Falcon 3.0 had a really nice flight model.  I think some of the best five to ten year old flight models are just fine.  I doubt MSFS's lack of a good flight model has anything to do with MS's inability to create a flight model.  Instead I think it's more a lack of attention in an area where most customers frankly don't care.

That said, MSFS's flight model feels REALLY good during normal, within the envelope flight (where most real world pilots, acrobats and military excepted, spend all of their time).