There’s a request for an A320 rework open, so why not do the same for the A321?
Long story short, the A321 suffers from essentially the same issues as the A320, as well as the rest of the family, having gone from a great aircraft that has had a few updates (such as wingflex and live cockpit), to an average aircraft as time went by and nothing but livery additions was done to it. The A320 family as a whole, while having live instruments, has otherwise terrible 3D modelling of the cockpit - compare that to the 737NG, which has had similar treatment to the A320 family, but features a significantly better cockpit - as well as lacking a proper interior and certain animations, such as doors opening, elevator trim and roll spoilers.
Specifically for the A321, it has been widely reported that its flight model is worse than that of the rest of the A320 family, being known to wabble under certain conditions other A320 family aircraft would likely fly just fine.
While not nearly as popular as the A320, the A321 has proven to be a reliable workhorse for airlines around the world in short to medium haul routes with higher demand than the A320 is capable of supplying, going on to crush the 737-900 and -900ER in sales, selling more than triple the amount of these aircraft combined. In addition, as more and more people fly, aircraft with higher capacity, such as the A321, become more desirable for airlines, meaning A321s around the world will fly perhaps for longer than expected. Lastly, it was the basis of the most popular narrowbody aircraft in orders, the A321neo and all of its variants.
Just like the rest of the A320 family, the A321 is a decent aircraft in Infinite Flight, however it definitely could use some love, especially regarding the annoying wabbling behaviour.