“Citadel” has the feel of an old-fashioned spy show, dressed up with sleek leads (“Game of Thrones’” Richard Madden and “Quantico’s” Priyanka Chopra Jonas) and state-of-the-art action.

It took almost five years between Amazon’s Citadel announcement in 2018 and the series’ premiere in 2023. It might take three more for Season 2 to hit the streamer. THR is reporting that the ...