When and if you want them to never of their own choice or when they come together with abilities that support each other in combos...
Oh yes, you mean these very narrative powers of push/pull/slide and balls which are actually squares on the map. No, thanks, I'll take the narrative combos of my players any time over these, like yesterday evening when a player distracted a Prince of Hell while the other one rummaged around the back of the command tent trying to find hints about what had happened to the orders that the Prince should have received multiple times.
just relying on crutches like anti-magic (also a game mechanic but yours as a dm)
At least it's a narrative game mechanic that means something in the game world, and not something that exists only in the technical world of little squares on a technical map and that does only a purely technical effect that has no relation to what the different characters could do. It's really top-down levelling, reduce everyone to the lowest common denominator because one is afraid of the brilliant spikes.
Its all about your DM control and power right... never the player
My current game is a total sandbox. The players are in control of armies and have "allies" in hell, they decide whether they want to go in the areas where there is antimagic, or the path that they will take. But of course, in 4e, everything needs to be labelled and technically correct to be put on a gridded map, everything needs to be codified.
I have seen how you improvise tactical benefits in our discussions I would not trust you very far without some tool...
OK, this discussion is over. First, you dragged me back into edition warring with your insistence that it had to be only a matter of taste, and second this is actually extremely insulting. Have fun with your 4e, but stop trying to peddle it to everyone, it's dead out there for many good reasons (that of course you will never accept because all the people not agreeing with you are idiots for not seeing the light of 4e).
And the vast majority of 5e DMS here are utterly erratic about similar things, most erroring on the side of against the player.
Yeah, I know, we 5e DMs are all erratic and stupid, railroading DMs with no respect for the players. Riiiight....