I think the 3e approach to level drain ("negative levels") solved a lot of issues- you didn't forget your abilities, they simply became weaker. You could lose spell slots, but you didn't forget what spells you could cast, and so on.
I don't have a problem with effects that reduce one's effectiveness (be it negative levels or ability damage), as long as they are temporary or within a player's means to overcome.
It's like running a wight, shadow, cockatrice, etc.. at low levels when the game tells us "yes, this is an appropriate low level enemy" but the players have zero ability to overcome being drained to 0 or turned to stone. To me, it always felt mean-spirited. Some of my contemporaries will point out that real life isn't fair, and things like this happen.
To which I reply, it's not real life, it's fantasy! Sure, I live in a world where I could be fired, shot, run over by a car, betrayed, or abducted by aliens at any moment, and there's nothing I can do about it. Why would I then want to deal with those same problems in a game I play for fun, unless I have the ability to do something about it?
Too often, I'm told "well, it's your fault for fighting such creatures or going into dangerous places". When going into dangerous places and fighting monsters is like, the whole point of D&D!
It's like my third game of Call of Cthulhu. After being told by the guy running the game that our previous failures were due to running into dangerous situations unprepared (and who really is prepared to encounter cosmic horror? John Constantine?), despite having dealt with a painting that simply looking at it can drive you insane and a "star vampire" that was invisible, indestructible, and could only be sealed by an ancient ritual, the setup for the third session was as follows:
"You have all been gathered to the reading of a will. Your college mentor, who guided you on the path to success in life has died, and you are all named in the will. You've traveled to the remote town he had retired to for the weekend. After checking into the hotel, you keep hearing people talk about "the murders" with quiet dread. News reports talk about a murderous cult in the woods. The next day, the Sheriff comes to the hotel and warns all the guests to stay indoors while they sort the mess out."
So guess what we did? We stayed indoors. No plot hook had been given to us beyond the reading of the will, and we'd all been told that it was dangerous to go wandering about. So we didn't. The weekend ended and the GM (I can't recall the term CoC uses for it's GM) simply shut his notebook and glared at us.
"If you're not going to actually play the game, we're done here."
To whit, if the point of the game is not to play it safe, and touch all the things and run around like the hapless teenagers in Scooby-Doo in order to have adventures, then "playing it safe" might not be engaging with the medium.
I've found, personally, that slowly inching one's way through a dungeon, searching every 5' square with 11' poles and detect magic for tricks and traps, having Standard Operating Procedures for every door encountered, always attempting to bypass monsters, waiting to set up ambushes, or engaging everything with ranged attacks might get the job done, but for me, it's incredibly tedious. So I assume that player characters are professionals and only behave in a reckless manner when they tell me that they are doing so- otherwise, nobody has to roll to find a trap unless there's a trap to be found, as an example. I assume everyone is wearing gloves or gauntlets when opening a door (just in case the handle has been smeared with contact poison), and if a ceiling obviously looks unsafe and might collapse if someone casts thunderwave, shatter, or fireball, I tell the players before they use such spells.
Some of my contemporaries think that the game is less fun when it's not played on hard mode. To which I say, some people like playing Dark Souls. Others like playing Elder Scrolls. There is no "right" or "correct" way to play the game as long as everyone is enjoying the experience.
