I'm not writing a story, I'm working with the players to create a story as a group. A narratively-fulfilling one. One that has a beginning, middle, and end. One that gives us ups and downs, ins and outs, an arching build rising up to a climax against the supervillain that has plagued the party for months if not years with a satisfying conclusion and denouement. And the reason I'm not "writing" it is because we are using dice to randomize certain aspects of the story. I have no control over those dice rolls, and neither do the players. Parts of the story are at the whims of the dice and we as a group will follow them quite often. All I can control is how much those randomized elements don't completely screw up the story for the worse. If that means creating a reason why the party cannot take a long rest immediately prior to the supposedly climactic final battle...then I'll do that. If that means having more minions come swarming out at the party in a couple rounds because the roadblock that I thought I was throwing up with a bunch of minions ended up being no roadblock at all because my guesstimations on how the party would be able to handle them were way off... then I'll do that. If that means the ritual that I thought would last for five rounds before going off ended up having to be postponed for a couple rounds because the party decided to monologue at the BBEG for a couple rounds before the fight even began and they were enjoying the back and forth with the supervillain... then I'll do that.
Assuming of course that I WANT to see a story like that at that moment in time.
Maybe I won't. Maybe I won't care. Maybe that one time I'm perfectly happy to let the party steamroll the BBEG in one round for whatever reason. But that's me reacting in the moment to what the players seem to be hoping for with regards to this fight. I mean, it's not that hard to see and learn when my players are thrilled by accomplishing a one-round curbstomp of an enemy, or when they are a little underwhelmed by how easy it was. So I'll play it by ear and react in the moment like the proper improvisor I am as a Dungeon Master and throw out additional offers to the scene to help drive it forward.
Now as far as your situation as you mentioned in your edit... if you think nudging the game such that there's a better shot at ending up with a five-round build of a fight that leads to a massive, skin-of-their-teeth, party barely survived, successful climax of a fight with the BBEG is contrived and lessens your enjoyment... then you don't have to do that. That's fine. There's nothing at all that says that's the kind of result you might want. If you want to play the board game via the board game rules and whatever happens, happens... that's great. But if that's the case, then there's no reason to ever be annoyed by the circumstances of what this thread is talking about, which is "control spells" supposedly ruining one's fights.
If you don't feel control spells are causing issues at your table and you are perfectly fine with any combat result-- ones that last a round, three rounds, five rounds, ten rounds or whatever-- then my post doesn't really apply to you. No harm, no foul. Instead, I was talking to the people who WANT a climactic fight with the party versus the BBEG when they decide they want it, but somehow expect the D&D board game to be designed to accomplish that by the snap of their fingers. Like the game rules can be built such that they receive exactly the type of fight they want at the time they want it... without them ever having to "write the story" themselves as you put it. Like it'll just somehow magically happen if the encounter is just "built the right way" using the game rules in the book.
Well... unfortunately that can't happen. That's not how the D&D board game rules work. The board game is just too complex and with too many variables to be able to be assured of getting a specific outcome. And no amount of rules design will accomplish it, especially when these fights are connected to one another with no way of knowing if and when the party can "reset" things. So if you want those outcomes to have a better chance of happening... you're going to have to rely on yourself and not the board game.
