Every predictable Black + Flame set made according to schedule causes the whole group of them to collectively lose appeal and feel less unique. And to be fair I'm not saying similar sets or overlapping themes across the entire history of the game are problematic, i'm saying doing them in such a trite and predictable way back to back is the problem.
I'm fine with TCPi recycling gameplay ideas in slightly different ways year to year because it allows them to slowly develop and iterate on ideas that people like without forcing people into expanded, but the "experience" each new set provides in terms of flavor should not be so copy/paste when unlike gameplay its the one thing that is almost entirely arbitrary (every set having to be tied to a marketable Pokémon).
Is it not only better, but also incredibly easy to actually surprise people with cool new themes (no matter how shallow these concepts may actually be) when they basically risk nothing doing so because they can always print Charizard whenever, wherever, and however they want anyway? Heck, even if you absolutely must have Charizard in the 3rd set due to demands from the corporate overlords to hit predictable market qoutas, why not Charizard + literally anything else? Brilliant Stars proved you can slot the Zard in at any time, in any theme (if not the entire history of zards in the game).