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I think the crux of it is not only the fact that common enemies at the end are notorious for having access to Defeat, which has a very good chance of BS wiping your party, but also the general non-linearity of the game. I'll admit that dungeons with multiple branches with most leading nowhere, riddled with a high encounter rate stresses me out to a certain extent. That being said, can you imagine how much more stressful it would be for a player in the 21st century if a game said "here's a boat, have fun!" ?
Briefly observing my friend's kind of games, to which he only plays new games, I feel as though people these days are used to having games which go from point a to point b. On their side however, I suppose it is rather tedious to explore a world, not sure where to go, and going to the wrong places usually results in enemies beyond one's strength to take out.

I just want to briefly go on a tangent here, which will ultimately lead to my opinion of DWII. There is this series that I used to be obsessed with, and still very much so hold close to my heart called Romancing SaGa. The whole premise behind it was to explore the world with a character you chose at the beginning, with NO purpose, rather than helping people, and do quests. Eventually, the enemies level up, and get replaced with stronger enemies as you gain strength, as well as certain quests losing accessibility as you gain power. In time, when you are at peak strength, you can choose to end the game by accepting an endgame quest. Some SaGa games even let you take on the final boss whenever you want, even in the first ten minutes.
However, beating the game is NOT the end, as you have to explore the world with the other characters, who in turn have completely different proficiencies, (although anyone can equip anything, exactly like FFII's level system) access to certain quests, start in different parts in the world, and can recruit different people (recruitment is totally optional, and up to you on who you want to recruit by the way. Character A from Story A can actually Recruit Character B,C,D,E,F from their stories for that matter). Where this all ties in is that non-linearity is an acquired taste, that is very bitter for those who aren't expecting it. The SaGa series are highly criticized by western players for exactly that reason, which is one of the reasons why we haven't had a western release since the PS2 remake of the first SNES entry, which you HAVE to check out, even if just for the voice acting, and legendary soundtrack.

Due to my love for Romancing SaGa, I enjoyed having to explore to find progress. Like I said, it was very bitter at first, as the enemies bit you hard if you went somewhere you weren't supposed to go, but I quickly learned the significance of talking to NPCs, who really do spell out where to go next if one pays close enough attention.
In terms of difficulty, there's no cheat button or even an easy button for this game; Hargon is going to breathe icy wind at you, and 3/5 times you're going to get hit hard, even with cold resistance. You're going to encounter three Green Dragons in the path to Rhone, and most likely get BS wiped if you cannot run away in time. And if you're me, you're going to take a Defeat spell full on, three tiles away from the save point in Rhone, and will have to redo the entire path to Rhone segment. These are just some of the nasty surprises that DWII offers its players, but it's not like it's the only thing the game offers. It is very generous with town locations, quality of chest content, helpful NPCs, and I'll even go as far as to say good dungeon layout, if you can outsmart the enemies, who all have their ways to do so.
Besides, being the music geek I am, I find DQII to have the best soundtrack in the series, and yes, even better than IV, my favourite entry in the series. I always get a little emotional whenever "My Road My Journey" comes on on my iPod, or I put "Travelling with Friends" on whenever I depart to the cold, barren, snow ridden landscape of Winter Canada, and hope no monkey jumps out and casts Defeat on me.

Like you, I started with the NES version, but since then I've played the SNES version more. While I do like the NES OST more, I play the SNES version simply out of convenience, as ZSNES is a great emulator. While the SNES version does have a few modernization elements to it, and slight item additions, there's not that much of a difference gameplay wise between the two by the end of the day, I find.
That being said, I did manage to get my hands on a hard copy of the SNES version, which I totally plan on playing someday whenever I invest in an SNES (played mine literally until it was a sparking pile of dearest memories), I figure I got through non-emulator NES DWII, so SNES shouldn't be too difficult, language barrier aside.

So yeah, that's what I think about DWII in a nutshell. There is so much more to unpack from this gem, but I should be focusing my interpretation and writing for my papers. Hope someone reads my ramblings!

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(warning, big a** image alert, 3.54MB image, to be precise)