I generally think that Blizzard does offer *solid* experiences for the most part, but they're also quite geared towards certain features from the ground up and aimed at rather specific audiences.
SC2's single player - mechanically - was generally fantastic. It's nice to have a nicely polished RTS with a tough Brutal difficulty level and a pretty huge skill floor to enter and a near infinite one to hone. The story had some promise but declined sharply with HotS, but I still appreciated the mission variety regardless of the rest of it, and some scenes were carried by their "cinematic" value, as is often the case with Blizzard stories (though some SC2 cutscenes were also pretty bad). It was also nice of Blizzard to reintroduce Brood War and give it some additional support, even though the implementation of that has been sketchy. Still, I enjoy listening to Tastosis while looking at the refreshed graphics during ASL. Blizzard has also generally been pretty generous with WC3 recently, having introduced a patch to give the mapmakers some quality of life improvements - and I doubt they get much revenue from WC3 anymore. Also, a lot of SC2's downfall came from utter neglect of Arcade modes (or outright mishandling those, as was the case a long while ago with their "sponsored Arcade maps" thing) and being horribly inaccessible, with the ridiculous 60$ pricing for three expansion packs and believing they will get most of their revenue by hyping up the game as an e-sport. Still, despite all of that, SC2 is pretty satisfying to be good at, just like its precedessor.
Diablo 3's launch was quite a travesty and there had been a lot of stuff to complain about, and I do agree that the Diablo 1/2 experience was way easier to customize for the purposes of a player who doesn't necessarily look for a loot treadmill. However, with RoS, the game genuinely looks, works and plays better, and it does fill up a certain, very arcade-ish niche. I can't get into Path of Exile at all in spite of it supposedly being perfect for D2 veterans, because PoE just feels extremely slow and the mood it's trying to set up doesn't give me the same vibe as D1/D2, as hard as it tries. Not denying PoE is a pretty superb game though. Still, D3 seems to have decided to go for the niche of just full-on arcade'ing and attempted to embrace the vocal portion of the fanbase that lived for the loot addiction. It also looks like a pretty good game to pick up and play in short bursts.
WoW seems to continue the trail set by the expansion packs and all of the content that's worth doing is in the end-game. Levelling a character is boring as fuck and even though the post-Cata early instances look like they have much more to do than tank'n'spank, it is kind of a white noise outside of that. I'm not too certain about what Legion's late game looks like and I'm sure someone could educate me as to whether WoW's mythic raids are shit or a fun challenge. Nevertheless, Blizzard seems very intent on focusing on the content that is most "current". It's problematic for those who are starting off or like levelling alts for sure, but if we assume WoW has been about end-game content since the last few expansions, you could argue Blizzard isn't doing badly there.
I like OW. It does have quite a surprising amount of depth to it, and there's plenty of characters that are challenging to play. I generally enjoy it because it's a fairly fresh experience depending on team compositions - running around as Rocket Launcher Lady or CoD Guy has some unique, fun elements to it when put in the context of a game full of tanks with barriers, Pudge-like hooks and whatnot - and the gameplay is generally good at constantly giving you something to do. I keep it installed alongside UT'99 for some fast-paced instagibs and what not, and I generally think it's a nice game, colourful, enjoyable to look at, satisfying to play, good for both dicking around and for furthering your skillset.
Though I don't care for lootboxes much - skins and whatnot are a nice bonus, but not something I actively strive towards - and I'm not particularly happy about the trend to include them, but I assume it's simply the climate of businesses trying to maximize their earnings. Ever since the days of Oblivion's horse armor and Fat Gaben confirming players are willing to spend lots of dollars on cosmetic items ("just to help support my favourite devs" or whatever your poison is), it seems like it's too late to do much about it now.
So yeah, Actiblizz? Pretty crummy company. What is their best modern game? Hard to say (I'd probably vote SC2), and it's very reasonable to say that their quality harshly declined with time. But, well, I guess I'd still rather give my trust to Blizzard than Bethesda, Ubisoft, Bioware and a handful of other companies. It's very limited and I generally look into their games with a grain of salt and don't purchase any of the "bonus" content - and in fact ceased any activity on Hearthstone after realizing going F2P is too much effort, but they're not that bad for an AAA fix.