I played the game without spending anything just to form an opinion and it legitimately has higher production values than Diablo 3. Voice-acting is top-notch, cinematics are nice, even the writing does not suck for the most part - my Crusader character actually sounds like an intelligent warrior during dialogue. There's also a ton of activities to do from early on, and when you hit Paragon even more quests and events unlock. And the whole "Immortals vs Shadows" pvp metagame is really interesting and could be the focus of an entire game on its own.
The first trouble starts after level 30-ish, when the game pretty much tells you "reach level 35-40 in order to continue the main story" which leads to the first required XP grind. And then you eventually get to the known monetization issues, and everything falls apart. After you hit paragon+30 or so, it is pretty much impossible to acquire the necessary gear to proceed to Hell 2 difficulty without buying stuff from the store (and then, as already demonstrated, spending money does not guarantee you'll get good gear), unless you grind like a Korean cringebot for 25 hours a day hoping that you'll get a decent drop.
I might pop in once in a while if they add new content or to do a dungeon or two with friends. But after a certain point in the game it is simply not worth the time investment necessary to proceed.