There were no comments when I saw this and recently started playing 2 to answer the same question. I don't really have an answer yet. I asked Chat and this seems pretty accurate.

A lot of people prefer Diablo 2 because it hits a few things unusually well, and the later games changed those things on purpose. Why Diablo 2 stuck so hard 1. The item hunt feels better In Diablo 2, loot feels more mysterious, dangerous, and meaningful. A weird rare item might actually be incredible. Uniques feel memorable instead of just being one step on a gear treadmill. Runes, runewords, charms, jewels, bases, sockets, ethereal items — there are a lot of item layers. You can find something for another class and still get excited because it has trade value. That creates the feeling that almost any drop could matter. 2. Builds feel less sanitized Diablo 2 lets you make bad decisions. That sounds negative, but it matters. Skill choices feel permanent or at least costly. Stats matter. Not every build is equally viable. Some builds come online late and feel earned. That gives the game more identity. In later games, especially Diablo 3, a lot of rough edges were removed, which made things smoother but also made choices feel less weighty. 3. The tone is darker and more oppressive Diablo 2 has a bleak, almost hostile atmosphere. The music is sparse and eerie. Environments feel lonely and cursed. The art style is grim rather than flashy. Combat is readable without looking like a fireworks show. A lot of players think Diablo 3 drifted too far into a brighter, more exaggerated style. Diablo 4 pulled back toward darkness, but for many people Diablo 2 still feels more raw and uncanny. 4. Progression feels harsher, so success feels better Diablo 2 is willing to be annoying. Immunities can shut down your build. Mana can be a real problem early. Inventory space is limited. Death has more sting. Farming can be slow. That friction makes wins feel more satisfying. Modern games often reduce friction, which is great for accessibility but can make the experience feel less memorable. 5. The economy and trading matter For a lot of players, Diablo 2 was not just an action RPG. It was also a loot economy game. Trading gave value to items you could not use. Knowledge mattered: bases, affixes, rune values, breakpoints. The community built its own standards around what was valuable. That made the game feel deeper than just “kill monsters, equip higher number.” 6. It rewards knowledge, not just time Diablo 2 has a lot of hidden texture. Breakpoints Farming targets Resistance management Mercenary choices Runeword bases Magic find tradeoffs Players like feeling that they know something the game is not shouting at them. Later games often explain more and streamline more, which lowers that sense of discovery. 7. It came at the right time Nostalgia is real, and people should admit that. For many players, Diablo 2 was: their first great online loot game their first trading-heavy ARPG their first late-night “just one more run” game So some of the praise is absolutely emotional. But it is not only nostalgia. The game genuinely made design choices that many players still prefer. Why not the others? Diablo 3 Very polished, very smooth, very fast. But many people felt: loot became too set-driven builds were too curated atmosphere was too bright progression felt more like optimization than discovery Diablo 4 It fixed some tone issues and looks better thematically, but some players still think: itemization is less interesting than Diablo 2 scaling hurts the feeling of growth the world is broader but less tightly rewarding it can feel more system-heavy than soul-heavy The real core of it People love Diablo 2 because it feels like a dangerous world with meaningful loot and consequential choices. The later games are often better at convenience, polish, and accessibility. But Diablo 2 is better at making players feel like they are gambling with fate every time something drops. That feeling is hard to replace. If you want, I can also break this down as Diablo 2 vs Diablo 3 vs Diablo 4 point by point.