To explain as well as I can, I've been trying for some time to find a very specific type of shooter, and it's very possible that I've already played everything close to it.
What I really am looking for is something between the slow pace of Squad or Arma, and the twitch-shooter of Call of Duty, Halo or Titanfall. In particular, I'm looking for something that makes your fights feel impactful or immersive, without having to spend twenty minutes walking (as much as I love Squad).
I'm also looking for something that is ideally single-player, but PvE works too.
Off the top of my head, the games that best match what I'm thinking of, is Insurgency: Sandstorm, particularly the 'hardcore' variants of their co-op matches, and Ghost Recon: Breakpoint, with the 'Ghost mode' on, with everything possible turned off.
My drawbacks from those two games is that:
With Insurgency, you don't have a single-player only mode (afaik), and the population of the game doesn't make these modes that sustainable anymore. I have more minor grievances with it, that really comes down to it being repetitive.
With Breakpoint, the game feels really easy after a certain point, and there's not really reason to change up your weapons. The open-world aspect too makes it a little boring and it falls into the loop of 'walk around, shoot a few people at this base, unlock some new gloves'.
Some other games that I have tried but don't match what I'm looking for:
Hell Let Loose - Perhaps the one I'm the most open to 'trying again', although I'm not super big into big PvP shooters at the moment, or WW2 settings.
Ready or Not - Tried it, played it. It was fun enough, but couldn't hold me.
Six Days in Fallujah - I don't know if I'm missing something, but when I tried this game I absolutely hated it. The game was super clunky, and the weird History Channel-vibe gave me flashbacks to playing America's Army as a kid.