As I personally haven't played UL for more than a couple of hours, giving my opinion here might seem daft. I have watched streamers/YouTubers play recently and it has convinced me to give the mod another go. I think playing it the first time somewhat blind was overwhelming. While it might look like 7DTD, it plays quite differently in some aspects. I think the largest hurdle for many players would be how much grind is involved. There are a lot of steps to do even simple things (no more crafting wooden frames in your backpack).
However, the mod also adds a lot in terms of QoL improvements (lockable inventory, broadcasted stage containers, etc), weapons (tons more guns, melee weapons, ammo types), materials (more ore types, more crafting items), game mechanics (weight-based inventory, lock picking, vehicle recovery), and vehicles (more variety in cars/trucks, motorcycles, helicopters, all obtainable). I think most players will tell you it feels like a more complete version of 7DTD. If going through more grind is something you either enjoy or see as a fun challenge, this mod has a lot of payoff.
As with most overhaul mods, it is highly unlikely you could get another mod to work properly along with it, especially a weapon mod.