it is what it is
I grew up with Diablo 2 and didn't get to play Diablo 1 until my teenage years. Ever since then I've made numerous attempts at beating it, but always gave up at some point. I think it has come the time to admit that I've given it more than a fair share of chances and I just don't find it enjoyable.
Going into it after D2, it was only natural to have lower expectations and an open mind, which did lead me to appreciate its innovations and the aspects it excels at. For example, as many have pointed out, D1 is a much darker game than D2 with a more oppressive atmosphere and the overall experience bordering on horror. I love the simple premise where a church leads you down endless tunnels into hell. The soundtrack is on par with the sequel and is one of the best ever.
However, despite D1 pretty much inventing its own subgenre, its own gameplay is very unrefined. The first few hours of the game are a constant loop of going into the dungeons, fighting a bit and going back to the village to sell stuff. This wouldn't have been a huge problem if the walking speed wasn't egregiously slow. Some mods and source-ports have solutions for it of various success, but if we're talking about the original Diablo, that's definitely a major problem. Beyond the boring and frustrating loop, there are cheap deaths. The procedural generation here is very rough and much more chaotic than in the sequel. You might end up abandoning a character because the procedural generation might fuck up your early game so bad it becomes almost unplayable. But even on later stages the game can be quite frustrating and unfair, partially due to jank. If certain enemies surround you, you pretty much have no way of saving yourself because their attacks are canceling your attacks, and obviously they're able to attack faster because there's more of them, thus soft-locking you until you die. The magic in the game is also pretty awful becaue you have to rely on scrolls that take up a lot of space in your inventory. Furthermore, a magician dies too quickly and can't do shit without mana, which makes him an objectively inferior character to the warrior.
Some people say they like how Diablo 1 allows you to use wrong weapons/armor and developing your character any way you want, but I think that kinda makes the whole idea of having classes irrelevant. Titant Quest would later come up with a better solution for this, but between D1 and D2 I much prefer the streamlined process of D2. There is no benefit to playing the game wrong, you're just gonna keep dying anyway, so it's actually a good thing that D2 implemented some guardrails.
In general, I'd say, as much as I respect D1 as an important milestone in the devlopment of action-RPGs, Diablo 2 pretty much improves upon its every aspect immensely. In fact, the jump in quality between D1 and D2 is one of the biggest I've ever seen in a game series. D2 is near-perfect and still hasn't been outshined in my opinion. D1 is an obsolete relic of its time that doesn't provide much reason to play it beyond historical interest.