2AP is definitely serviceable in some cases, but time units is a whole new world.
I’d also add that TUs are more simulationist because it is able to take into account things like facing direction. While 2AP’s simplification tends to go the opposite direction and makes combat more gamey.
I personally found 2AP the way XCOM did it to be a lot of fun. But they are very different games.
XCOM 2AP are fun indeed, they just make the games feel more like board games rather than "simulation" of combat scenarios.
Which is fine of course, just a lot different that what the old UFO/XCOM games were
XCOM 2AP is a big reason for why so many players express frustration with it (relating to the RNG), imo. You have very few actions per turn (early on just 1 attack and a move, or a sprint and no attack... Later on possibly a free attack or two based on skills with cooldowns) and few ways of mitigating the RNG (mostly skills/grenades and some mods).
Add a small squad size and lack of flexibility (class-based system with lots of restrictions, no real inventory beyond a few slots, most of which don't allow more than 1 item class or 2).
Such a system works better for very large squad sizes (basically panzer general and such games, not really squads anymore) to keep turn time down, but of course all the slowdowns in xcom (esp. xcom 2) and the sluggish u.i. negate that upside entirely.
The combination of few actions + few units + no solid, readily-available "counter RNG by spending action points/TU" mechanic = every failed shot is extra annoying.
For small squads JA2's system is way superior.
For 12+ guys in a mission old xcom does it better, and is also way more flexible in terms of what tactics you can use/loadouts.
Old U.I.s can be improved, xcom can get kneeling/standing the way JA2 did it (click on and drag your guy up or down to change stance) as well as targetting (point roughly at head height of the enemy to aim for a headshot, torso for center mass, leg height for leg shot if necessary... Right click on target to change single shot accuracy or full auto round count or accuracy if the former is not implemented in-game).