It's unfair of the developers to take away physical Artillery

[Mune]

I read the OP but don't have time to read the many pages of replies. So, if this has already been mentioned, my apologies.

I'd say the issue gameplay-wise with artillery (in a fundamental way, as in it can't really be balanced without removing artillery) is not that the victim has no LOS of the source, since that's a common enough occurrence that is part of all FPS games (snipers, getting flanked, etc). Rather, it's that the artillery doesn't have any LOS of their victims, since they just lob their explosives at a high arc and watch for kill notifications. This makes for a much less emotionally rewarding experience than gunning down an enemy, where more tension and danger is involved thus improving the joy of victory.

It's delving a bit into psychology, which is always a gray area with lots of room for interpretation, but I can see why a dev looking to attract players might opt out of having artillery in their game. In a game where conflict between real players is the main feature, someone has to win and someone has to lose each conflict (as in, one will kill the other). Dying in an FPS isn't the fun part, and lets be honest, when we die too much we get frustrated and look for reasons (logical or not) as to why we are dying more (other than a lack of skill). On the flipside, the little victories in games of conflict are what keep us having fun, and killing an enemy is the most directly rewarding experience that FPS's have to offer and what makes it such a popular genre. Fictitious gameworld or not, the adrenaline of defeating an enemy who was equally devoted to trying to defeat you is what makes FPS's fun.

Simple logic I'll state for the sake of thoroughness, but the joy of victory needs to outweigh the frustration of defeat in order to make for a popular game. The idea of artillery doesn't fit into this concept quite as nicely as the other aspects of FPS games (namely, shooting the enemy). I would argue that killing an enemy you didn't see via artillery doesn't provide enough enjoyment to overcome the frustration of being killed by said artillery. Sure, artillery kills are rewarding and it takes some planning to accomplish, but on a fundamental level, it is not as exciting as a gun battle. I bet if we were to measure the adrenaline levels of someone using artillery versus someone in a gun battle, the difference would be statistically relevant.

TLDR, if I were one of the devs, I'd bet more people would avoid the game due to the inclusion of artillery than would avoid it due to the lack of. It would be a risky bet, but I'd probably be correct, and I'd have more players/money because of it.