I am splitting the review into story and post story parts, since I felt the quality was largely different for each part.
Playing through Diablo 4's story was really great fun ! Amazing cutscenes introduced a grim, dark and very Diablo 1 like game, in very decent and in parts impressive graphics, that has the most amazing soundtrack since Diablo 1. Shortly after I took my first steps, my Necromancer found their first challenge in form of a large bear, while the snow storms where whipping up an amazing atmosphere. I stumble away from combat into the nearest village. The stage is set for the centerpiece of the story and shows some aspects of whats coming later in the game. We get a glimpse of the demonic, the depraved and hellish shenanigans the hell-spawns are up to this time in Sanctuary.
Fast forward, around 30 or 40h later, I find myself enjoying the Necromancer's skills, enjoying a neat setup of summoning and blood spells as well as a few powerful items I found during my latest adventures into caves and dungeons and dark pits of doom and death! I feel the end of the story approaching, enjoying main quests a lot and some of the sidequests as well. The world seems a bit empty in parts and in other parts nearly crowded. The game feels mostly like a single player game and I am very happy with that. Other players do occasionally pop up, making me wish I could just hide 'nickname' to not break through my atmospheric immersion so much. It is not a big deal most of the time though.
A very modern game that captures some of the very oldschool Diablo magic and that managed to pull me in with its greatest strengths: atmosphere and dynamic flow. I always felt like an explorer and sometimes also like a powerful hero, going against all odds and the unfathomable forces of hell. I felt like a treasure hunter at times, when the rare powerful items dropped and gave me new powers or modified my existing ones to some extent.
It was one great week spent with an action adventure game that had light rpg features, some loot combined with a neat progression mechanic, character specific extras and lots of enemies in various locations all presented in splendid look, accompanied by awesome sound design, a great soundtrack and fun gameplay. Some of the boss fights were great! Some vistas were breathtaking. Fun times!
Directly after finishing the story I found myself standing in the large world of Diablo 4 and was completely lost as to what to do, where to go and how to proceed. It was like someone cut my lifeline to the previous experience, the feeling of being in 'that world' and making life hard for demons and unlife harder for the undead roaming about. It was all gone. *poof* That does not stop me , Nemo the Discoverer! So I took a walk around Post-Story Sanctuary and was....left feeling sort of....underwhelmed.
I found dungeons to be a fun way to pass the time, collect some random-ish legendary aspects to use in crafting. I saw some world events happen. I saw the random quest-collectathon provided as a means of post-story questing helper. And it all felt rather empty real quick. I know that grinding levels and gear is what some people love. I think the paragon board was a neat idea for sure!
I have one serious issue though, the items in Diablo 4 are a total mess. After leveling up 5,8 or 10 times I often found myself using the same gear. I did not switch my skills anymore after some time mid to end of the story playthrough.
The nearly as serious issue number two for me, was the fact that progression for my character came to a stop. After hours spend I might level up once or twice. I do not want a fast train to maximum level, don't get me wrong. I want to feel some form of progression though, something tangible to motivate me to go forward. I do not want to be forced to play in a party of random strangers to get more xp. And yes I was using the XP Potion boost....
That is not what I expected from an ARPG in the Diablo Universe. I was hoping for more, especially since the story was really, really good fun and I loved the presentation and some of the sidequests and dungeons so much. Currently, I cannot bring myself to spend more time in Sanctuary, but I would still recommend the game for the Story. Its a great time you can have there, just do not expect any depth from the game after the story ends in terms of ARPG gameplay along the lines of the great Grim Dawn, Path of Exile or Last Epoch.
Disclaimer: This was all pre-patched Diablo 4. I am hoping that things improved!