The fun is in the game throwing you in an unfamiliar environment, stripping you of your equipment, and demanding you complete the objective using all you've learned about the game so far to do so.
The execution is the problem, they tried to crowbar a Hitman clone into this single quest when the game already has a hard time working normally and the results are as you'd expect.
Maybe it is because I played it only few months back with all patches, but I had no problem with its execution and enjoyed it thorougly.
As someone who played that quest within days of release (Steam achievement says 19 Feb, and release was the 13th) I can say that while it DID work, and while I did enjoy it, it's also the point where you could see the game beginning to break under the weight of its own systems. Events in the quest would sometimes trigger, and other times wouldn't, seemingly at random. I once had the monastery residents all gather in the courtyard with an announcement made of a need for extra guards, which I believe is only supposed to happen when a murder has taken place, but I hadn't murdered anyone. Reloading a save from maybe fifteen minutes earlier stopped this from happening, and I was able to continue the quest without the hindrance of extra patrols. Some aspects also feel poorly explained, and I'm never sure whether or not the intention was for the player to
discover what the limits of monastery life were, or whether the devs just didn't explain it properly. A good example is the ability to skip Matins, or any prayer session, by simply showing up at the beginning and making sure to be there at the end. This, seemingly, allows you to use this time to go snooping around, but also sometimes it doesn't and you get yelled at.
Ultimately, the problem with the quest is that the best way to deal with it is to just bust in and murder the relevant person by looking at a guide online and finding out who it is. Not even looking at a guide and following the precise instructions, but just looking for a picture of the NPC, finding him in-game and murdering him.