That was kind of tedious, actually. I blasted through season 1 in next to no time, but had to slog through season 2. They're aiming at tragedy, but I think what they actually achieve is "what a load of idiots".
We left season 1 with a three way ghoul-ghoul-human war having been put on hold for an episode of Kaneki getting tortured beyond all imagination and twisting his morality into odd shapes. "If bad things happen, it's the fault of the victims for being weak." Yeah, right. Kaneki then decides to protect everyone by helping kill a ton of police officers over a prolonged period as his equivalent of going to the gym, thus helping to inflame the human-ghoul situation even worse than it already is. Then, at the end, he at last has a conversation with the one person who could have talked him down from all this, thus receiving some laser-guided observations on how his thinking was wrong. Yeah, we spotted all that. Too late now, guys.
Kaneki so glaringly fails to achieve anything that it becomes the point of his story. He's a direct cause of the destruction of what he wanted to protect. His intelligence downgrade (and his disappearance from the spotlight) also deprives the series of its protagonist and makes it feel kind of directionless.
The storyline, so to speak, is more human-centred this year. We follow assorted characters. Lots of cops, one manic psycho child, the investigator daughter of someone who died last year, etc. They're all either doing their (semi-evil) jobs or driven by revenge. In other words, no one has a story that's moving things forwards. Sometimes we return to the ghoul side of things, but the nice ones at Anteiku have nothing to do except get on with their lives and angst about Kaneki (ahahahaha) and the nastier ones at Aogiri go largely unexplored. There are quite a few mysterious ghouls that clearly have backstory we never learn about here.
I'm pretty sure there's still some manga story that went unadapted, by the way. The circumstances of Kaneki's ghoulisation are deeply suspicious, e.g. the doctor who operated on him somehow managing not to notice that his organ donor (being a ghoul) would have been immune to being cut with knives and scalpels. Does that get addressed this year? Nope. We're also told that other ghouls beyond Kaneki have been converted from humans, so it's not as if the question isn't being drawn to our attention.
This wouldn't be so bad if there were a third season planned, but I believe they've reached the end of the original manga (albeit with lots of changes). There's a manga sequel series, though, called "Tokyo Ghoul:re". Maybe they'll adapt that.
What the series is good at is making you feel compassion for the people on all sides. There's a lot of pain to go around and some tragic backstories. I loved Shinohara's coffees with Yoshimura. This underlines the pointlessness of the battles. One character even questions the meaning of his own fight in the penultimate episode. Unfortunately the show spends a lot of time on these deliberately pointless battles, which can get repetitive. I didn't really care. Stupid people are killing themselves through their own stupidity. Yes, and?
It's a mood piece. It feels as comes from a place of depression, which can admittedly be powerful for the right audience (c.f. Neon Genesis Evangelion). People take everything upon themselves, can't bring themselves to share and can't stop hurting each other. We're cruel and we don't even realise it. We eat our loved ones. The show's painting human relationships as doomed, either by our prejudices ("ghouls are evil"), our pasts (so much of this that it hurts), external forces (love is star-crossed in the Tokyo Ghoul universe) or simply our inability to embrace what's in front of us (I won't say who).
There's admittedly some strong material here. People taking decisions this extreme are going to be saying a lot on the themes. Putting together in hindsight the chain of events that led to the final apocalypse is a delicate and horrible thing.
I think it's a heavily flawed piece of work, but one that will probably speak strongly to particular people. Personally, though, I mostly stopped caring. The plotting's driven by the season's preordained destination rather than by the actions of a protagonist. Characters are driven by philosophies so very, very stupid that it's kind of annoying. I'd still recommend the 2014 season, though.