That's a tough one because I've played first person shooters too so I can't put myself in their shoes.
I'll bring it back to the Pokémon statement again as well (not that I even care for the franchise). You can have a child in Kindergarten or a retired older person who never played a video game before take up Pokémon and turn-based combat in general and succeed without much investment. It requires no skill, dexterity, experience or reflexes to play.
I play games from pretty much any genre and had played RTS games before, but even I had difficulties with RTwP initially and I don't think it's something I'll ever master or be proficient with since I don't play frequently enough.
Edit: Again I don't really have a horse in this race, since I don't usually care what the gameplay type is. I just want a good game in general and from what I've seen I personally think it'd be easier/less time consuming or resource intensive to make the game turn-based.