People made this same annoying argument about Diablo 3, that the 'real game' starts once you've finished your first playthrough. But like.....that's lousy. This isn't some 6-10 hour game you can breeze through to get to the replayability. A single playthrough takes quite a long time, so why on earth could they not make that initial playthrough enjoyable as well? And not everybody plays these games to go through them 5+ times. I dislike 'endgame' loot RPG grinds. I might play through a game again to experience a new character type, but I'm not hanging around for the endless number chasing to where it starts to get ridiculous like in Diablo 3.
Diablo 2, for instance, could be played through just once, and you could have a lengthy, moderately challenging experience, where you could walk away afterwards satisfied if you never played the game again.
Or a game like Grim Dawn solves this by offering both a Normal(bit easy, but not too much) and Veteran option(bit challenging, but nothing overly so) for a first playthrough.
These games actually respect your time and understand that not everybody wants to play for 50+ hours before they get to the so-called 'real game'. And then remember that expansions will come for Diablo IV and make that first playthrough a fair bit longer still...
Diablo 2 on Normal difficulty wasn't that hard. You could get to see everything in maybe 8 to 10 hours, and that was it.. story wise.
Hell was difficult as hell though, 'cos your resistances went down a 75% and you had to compensate for that. You needed crazy good equipment. Even so, if you found a Lighting Enchanted Multi-shot super unique, you were done for.
Maybe Diablo isn't your thing, 'cos the first playthrough won't get you all the cool stuff. I agree with you with the "real game", 'cos it's a concept I don't like.
Heck, Diablo 2 -or Diablo 3, and I guess Diablo 4- was completed once you had beaten Normal difficulty. But tbh, the fun of Diablo is getting to higher difficulties to obtain the best items for your build and make your character even more capable.
Items like the Ribcracker for a werewolf druid were obtainable in Nightmare, but some Set Items, and Unique items, etc, could only be obtained in Hell difficulty, beating the most difficult bosses in the game or in level 85 Areas.
That's not the real game, but Diablo is sooooo fun 'cos of that, the constant challenge.
You could beat Diablo 2 in a jiffy with the help of friends, and most people did so,
thus you could get to Hell difficulty level, and you always wanted to play in that difficulty. The fun is there, getting the best items you can obtain.
Diablo 3 added some fun stuff to do other than playing a difficulty level like Hell all the time. The idea, imho, was great -this comes for a hardcore fan of Diablo 2, always in my heart-.
The good thing about Diablo is that you can beat it in Normal difficulty and see how the story unfolds, enjoy the super atmosphere, the great music, the dark setting, then never play again, or improve your character and play for thousands of hours trying different builds -now is easier than in Diablo 2 days, where you couldn't reset your stats-.
cheers