Mistwell
Crusty Old Meatwad
Sure if you really focus on your DC, which is a totally legit focus, then it has it's uses. A Divination Wizard who finds they have a low numbered Portent left near the end of the adventuring day might want to use it too for a guaranteed lock-down for a round.Actually, Tasha's has its place even at higher levels (though not, as you point out, if you neglect your save DC, and certainly not as your primary tactic). A lot of bruisers have crappy Wisdom saves, and a 1st-level spell slot to remove an enemy from combat for a few rounds is extremely efficient. You wouldn't use it in a boss fight, but if you're trying to conserve firepower on the way to that boss fight, it's good stuff.
The problem of course is not only is it single target, and not only does it have no effect on a save, but the target gets a new save at the end of every round, and also any time it's attacked (and the later save is with advantage). So it's really not a "reliable" spell even with a high DC. It also has a short range of 30'. So you're not even taking down a target that's fleeing with it.
For me, I find I tend to drop Tasha's from my prep list eventually. There are just too many spells my Wizard needs to prep which take priority.