Maybe I am willing to look into the logic of the games but:
D2 and D3 differences and similarities
Similarities
- Level a character making them stronger
- Harder modes upon completion with better gear
- Grind gear for hours looking for a good piece / stuff to trade and sell
- Can play solo or with a small team
- Can scale the monsters
- Can combine lower gems for better ones
- Shrines
- Gear was pretty RNG random
- In today's standards both stories were/are "meh"
Differences
- D3 had an AH, D2 had fan sites and spammers trading/selling gear for SoJs or money
- D3 you have to stack rare kills for better magic find, D2 you ran X act quest over and over and over.
- D3 you have a simplified talent build, which people just copy the top 1-3 online. D2 had a complex talent build, which people just copy the top 1-3 online.
- D3 you can see every drop others got making you feel even the great gear you got was sub par. D2 you only knew what friends got and thought what you had was pretty good. When in reality it was subpar.
- D3 has drm/online needed, D2 had offline mode, though plenty still played online for leaderboard.
- D3 has paragon leveling to add in something else to grind, D2 just had a long grind to hit its max level.
When you really look at the differences, you notice they truly are not different, but different paths to a similar outcome. Outside of DRM and people liking to play solo, most arguments that people make that D3 is "weak" can be shown in the same thing in D2. The differences being, blizzard streamlined a lot of the things the community did to be placed in the game anyway (simplified talents, AH, etc.)
The biggest issue is it is not as noticeable, since when D2 first came out, information on "builds" were not as well known, and thus the potentiality of many unique builds were created. By the end of D2 (10 years) there were set builds you had to run to be max efficient. This is because of every online game out there, people have learned how to quickly maximize each and every class in every game. And then its posted everywhere online. And everyone copies it, because its the most powerful build.
The only way D3 would ever in the eyes of the "haters" be considered better than D2, was if it was released at the same time; in the same infancy of the internet community and online gaming and D3 didn't have DRM. If blizzard was to release D2, with better graphics. Change the story and the names of everything, and pictures of the locations to hide the fact it is just D2 over again, I bet you would see as many if not more complaints about it being not "up to snuff" of D2.