There's a couple of things that go into this.
First, getting through a whole level undetected and unsuspected provides a real sense of satisfaction.
Second, blackjacking guards throughout a mission makes it easier as you progress. So you have this weird inversion where the difficulty ramps down instead of up over the course of the mission, and finishing it feels anticlimactic.
Third, you're not supposed to get spotted. It's kind of the point. If you alert guards, sure, you can go on ...
No downvotes from me - everyone is entitled to their opinion.
I play some missions (won't name them here) that have rave reviews that I uninstall within 15 minutes of starting,
This one (for me) was a weird one where I thought the beginning zone was very basic but somehow I got into it. I don't ghost so maybe that was a factor in me eventually liking it.
This mission is absolutely insane. Insane in terms of quality. Shows again that PukeyBrunster and Tannar belong in the top 3 of FM authors, after their near perfect The Scarlet Cascabel. I would even say that The Scarlet Cascabel is the best fan mission I ever played, and, this is of similar quality, albeit very different in terms of setting, of course. Although this is a "seasonal" fun mission, it's very thoroughly thought out, and coherent in itself.