I had a BCM Gunfighter Mod 1 that I got rid of for pretty much this reason. It wasn’t so much the angle as much as the size of the grip, or lack there of, that made it harder for me to grasp when running it one handed when compared to my MIADs that I was running on my other guns. I have a Mod 3 now and the larger size is much easier to work with when firing one handed so it will stay.
I hate the more vertical grip angles. I need the grip to be further back so the entire weight of the rifle doesn’t rest on my middle finger when doing one handed operations. I use a MAID for this reason on my rifles.
The MOE and most other more angled grips do offer better one-handed control, but it’s not as though it’s impossible to manipulate one-handed with a more vertical grip. What wears on me more is using the rifle for extended amounts of time with an MOE, A2, or any other grip like that. My wrist hates it.