OK, I'll concede 5e has made one monster more challenging, and in interesting ways. Good stuff.
But - is this the exception that proves the rule?
No idea, but if it is an exception, then it should show that the issue is far more complex than "5e is the least challenging edition ever"
In the ebb and flow of any RPG there's going to be times - sometimes lengthy times - where what's happening to one's character isn't fun. So?
Fun and unfun needs to be balanced. If there are enough parts of a fight or a situation that are not fun, then the players will simply ask the DM to avoid those aspects. Or the DM will avoid them naturally.
The Astral Dreadnaught in 5e has an attack that auto-kills a PC if they crit. I'm never going to use that, because straight up saying "you are dead now" because of a lucky roll isn't fun for me. It also doesn't challenge the player. What challenge is there in watching me roll a natural 20 on the dice?
I'm not saying everything has to be easy cakewalks, and I don't believe 5e provides that at all, but we can look towards what is an interesting challenge, and what is just aggravating and try and lean in the direction of the most fun for the players.
And in 1e it lasts for half an hour or so, if memory serves.
Not all the nerfing happened in 5e. Each edition has contributed its share, with 5e merely being the (thus far) culmination of the process.
My point is that, in the case of Ghouls -and Ghasts - they've gone from deadly to nowhere-near-as-deadly. In 0-1-2e if you got paralysed and your party couldn't save you (usually by defeating the Ghouls), you were done, period. You did not want to fight them unless you absolutely had to, or unless your party was mostly or all Elves.
Above, you paint them as being much more sporting.
I don't get the value in a monster the players will always want to run from. If they are hired to clear out a crypt and the DM lets them no Ghouls are inside it, do the players just return to the person who hired them and say "Nope, we don't want to fight them."
Maybe in some games, but I don't like that. And, I don't think the ghouls are that much less deadly that the party isn't going to try and come up with a clever plan to tip the fight in their favor.
But, I think the idea of sporting is important here. It is no fun to be told to leave the table. If your character is paralyzed with no hope of recovery, whether for a half hour in game or a minute in game, then you are done playing. Get out your phone, make a food run, whatever. Your contributions to the game are finished until the game tells you otherwise.
I don't see any value there. The player didn't get to decide, they made their character and tried to avoid getting hit as much as possible. And now they are simply a spectator at the table until told otherwise.
Doesn't the death of the caster in any edition break the spell? (I can't remember if this is RAW or just how I've houseruled it forever)
No idea
Except it's not that simple. There's more routes to success and fewer routes to failure that lasts anything longer than a few rounds...which also reduces the challenge.
Look at it from the Ghouls' side. In the past they only had to paralyze each PC once and >voila< they had a good meal. Now, with PCs so much more easily able to shrug off the paralysis, the Ghouls are playing their own version of whack-a-mole.
Who cares about the Ghoul's side? I'm the ghouls and TPKing a party isn't exactly good for me. It throws the entire campaign off the rails and I might even need to just start a new campaign because the story involved those people who are now Ghoul poop.
And frankly, they still can take a player down in moments with paralysis. Remember, each strike on a paralyzed creature is a crit. That means that a pack of ghouls goes from dealing 7 damage on average per attack, to 18. 4d6+2 per bite on a paralyzed target. They are still a massive threat, and since it is likely the person best suited to avoiding the paralysis that got frozen, then the party is going to scramble to find alternates and save their tank.
Again, maybe challenge is subjective. Anything where I have no choice in the outcome isn't a challenge. The Lottery isn't challenging to play, even though you fail most times you try it.