So, part of the reason 3e and 4e skewed in the "you always get to use all your toys" direction had to do with 2e's fondness for "if X causes a problem, just screw it over somehow."
The solution I think isn't the 2e method of "Hahahaha! Now you can't turn undead, sucks to be you, Cleric!" That
sucks.
And the 3e/4e method has its issues, too ("Hahahaha! I can turn Strahd!"). That sucks, too.
Then what is the intent here?
The idea is that everyone who is playing in an RL game is signing up and willingly playing a game of gothic horror fantasy where the villains hold all the cards. Someone who is choosing to play a Cleric in that setting should have their Turn Undead feature do
something, but we also want for it to do less than it would in a typical D&D game. That is, we want it to have a use, but not be the I Win button.
What about the typical TU makes it an I Win button? The fact that undead flee, or are destroyed is a big component of that. The idea with that initial design is that undead run from sources of goodness and light (like the cleric), and that bright enough light can destroy weak undead.
What if we just made a variant TU that worked a little more....defensively?
Then we'd have:
In Ravenloft, no light can fully pierce the shadows that make up the world, but certain torches can sometimes stand for a time against the coming tide of darkness. Turn Undead thus works differently, here: a cleric who uses this ability creates a zone centered on themselves that lasts as long as they concentrate and are completely still, up to a maximum number of rounds equal to their Wisdom modifier. Undead who wish to enter that zone or to produce effects in that zone must make a successful Charisma vs. Wisdom attack. If successful, the cleric's concentration is disrupted and their zone falls until they take an action and spend another use of Turn Undead to recreate it. A cleric in the mists thus can serve as a bastion for a time, though if their confidence wavers and their fear resumes, it will fall, allowing the hoards in.
...so imagine a high moor on a dim twilight where the adventurers are walking, and a
sea of zombies suddenly unearths itself from the ground and clutches at their ankles, dragging them into their own graves. The party cleric prays for some help, and a pale yellow sphere envelops her and her party. The zombies don't stop scrabbling, though, amassing at the edges of the zone, pressing in, like children on the glass window at a candy store, eager and hungry, and the cleric understands that this intercession is temporary, it is even now fading as the dark powers assert their control, and...those eyes...is that...the Wight of the moor's owner, his face a hideous rictus. The cleric gazes into those eyes for a moment too long, knows that they see the seeds of doubt that make his faith waver, and suddenly the pale aura shatters, and the wave crashes into them....
The Dark Powers thus pervert Turn Undead, as they pervert everything. It calls attention to the user, and causes hoards to swarm around, and keeps the priest standing in place. Really, it often winds up being more of a dinner bell than a defensive ward. But a clever cleric or a brave cleric can use it to take one last futile stand against the tide...or to try bargaining with the vampire for a moment...or to perform last rites on himself before the mummy crushes him...
Ultimately, the idea is not to bone the character out of a class feature, but to give them a new tool that is in keeping with the setting's ideas.