On non-AX Xeno-related activities, we indeed crossed the "let's get friendly" border two wars ago. Because a "virus that corrodes and destroys you so hard that even the person who shot you with it regrets it" is kinda hard to get over it. Plus, an ancient race that can literally just go away and await the eventual death of a species caused by the species itself probably doesn't see value in making friends.
Frontier painting Thargoids as the common enemy is okay, and it's not like this doesn't create interesting stories. The Starship Troopers references are great, what better way of talking about facism organically with that tangent? Chef's kiss.
Also, even for those who don't want to do AX but still want Xeno-related, there are still Reactivation missions (killing Thargoids there isn't required) and mining rescuing humans from Titans (which now is easier since Hunters don't interdict in Malestroms anymore), among others like supplying resources and transporting people away from the frontlines. These can still be roleplayed from the point of view of "having to clean up after warmongers" without attacking Thargoids, only helping humans who have no blame but are still victims in the war.
Heck, non-AX has more options than AX if you look at it. AX can shoot Thargoids in space, can shoot Thargoids in conflict zones, can shoot Thargoids on the Titan or shoot the Titan itself, and can shoot Thargoids who don't shoot back at the spire sites for cash. Non-AX can ferry humans away from the frontlines evading Hunters, can rescue humans from Titans, can reactivate settlements right under the nose of Thargoids (or recover important data from said settlements), can trade supplies to help those in need... Non-AX has more variety in activities than AX does.