Some valid points from a forum post by DEHowie, a real world Airbus training Captain:

https://www.avsim.com/forums/topic/620248-fenix-a320-engine-out-weirdiness/?do=findComment&comment=4792172

– Speaking of old lets talk Prosim which is the base for Fenix it itself is extremely old with literally being at least 20 years old as a basis meaning most ECAMS have had extensive modification by Airbus. In short many of the failures are inaccurate with incorrect ECAM information. ECAMS are continually updated as systems develop and change so unsurprisingly Prosim is a long way from a modern Airbus. It might be approved but hey so is the B-17 that doesnt mean it represents what a modern Airbus is like.

– The IRU panel/system in the Fenix hasnt been installed by Airbus in over 20 years and the old panel ie keypad etc isnt even compatible with a modern IRU. You see the IRU’s in the A320 needed to be modified for the approval of RNP AR as the IRU’s in Fenix represent a version long gone from Airbus. Since there replacement the IRU’s have been upgraded twice and the analogue panel is LONG gone from the overhead. The Fenix as presented cant even fly an RNP AR as its IRU’s are not correct, neither is the overhead panel which are swapped out with the IRU upgrade 15 years ago. So either the systems wrong or the model is wrong. Whatever the case its wrong end of story.

– Fenix climbs beautifully at 15 degrees nose up “ON ONE ENGINE”. In a real A320 if you even tried to climb on one engine at 15 degrees id give you under 20 seconds to still be on this planet. Its impossible for the real aircraft to do, end of story.

– How broken well thats easy id recommend everyone saying its not broken go do a simple test. Grab the QRH go to the unreliable speed checklist find your weight and set the power and attitude let it stabilize then watch what happens. Yes you get a speed nowhere near that your supposed to. yes the flight model is broken.

– Its broken what else does that mean [sic] it means the N1 on final is wrong, the drag model is broken, the fuel flow is off by a mere 40-50%!

– The control feel on it is nothing even remotely like flying a wingertip driven A320.

– Fenix was marketed and talked up as being the “ultimate” Airbus and its a VERY long way from that indeed.