@Taral: I thought it was very light on mythology, which was especially frustrating because there were avenues that could have been explored, but were just dropped (i.e. Snoke, the Knights of Ren, the First Jedi Temple).
The sincerity was hurt a lot by the humour for me. The sincerity is one of the things that really sticks out to me in Lucas's Star Wars films. It would be so easy to poke fun at things happening on screen, but it's played straight. Sure there's humour, but it's approproately placed. When it needs to be serious, it is. Take the duel between Luke and Vader in ESB. It's honestly kind of cheesey, and goodness knows it's been parodied to death in other media, but because it's played with such sincerity in the original, it's actually emotionally compelling. There were many moments of misplaced humour in TLJ that ruined the scene for me. Many ruined scenes ruin the movie. The actors did well with what they were given and any sincerity that came through did so in spite of the script imo.
Heroism is an interesting one and I think it makes your point ring the most true. I remember thinking that this felt like a move that was taking a shot at the concept of heroism because Luke is deconstructed as a hero, Finn's heroic sacrifice is interrupted, and Poe's insurrection is portrayed as hot-headed and foolish. Honestly though, I don't think I would mind the Poe and Finn thing in isolation. It's the characterization of Luke that casts a negative light over the whole film for me and then I see those instances as just more reason to dislike the film. I will always prefer a heroic sacrifice over an interrupted one and the message of "Shut up and do as your told because the people in authority know what they're doing" seems very un-Star Wars to me, but if Luke had been portrayed differently, I would have been fine with them for the sake of variety... especially because this is the middle act of the story. A similar thing to what happened to Poe in TLJ happened to Luke in ESB (e.g. going against the advice of Yoda and Obi-Wan, rushing off and trying to be the hero, but failing miserably) after all. And also Finn's failed attempt at a heroic sacrifice is offset by Holdo's actual sacrifice which was glorious.
In some ways I don't think the creators of the ST understand romantic story-telling. Things like Han and Leia being estranged in TFA and Luke being a burned out old man are very jarring in their cynicism to me compared to the fairy tale-like quality of the originals.
The hopefulness of the original Saga being undone. This movie made me feel depressed for a couple days after seeing it. All of the Lucas films left me feeling uplifted to some degree - including ESB and RotS, which are full of darkness but there's still an ultimate feeling of hope by the end. You could say that TLJ ended on a hopeful note, but I was so burned out by everything that preceded it, that it barely left a ripple.
And finally whereas the Lucas films felt like they had an ancient heart underneath, TLJ felt... I don't know the exact word... someone more versed in modern philosophy could better describe this... but it felt post-modern, nihilistic, or deconstructionistic. An easy word is "cynical". ESB and RotS were dark, but I don't think I would call them cynical. Same goes for R1.
Where sky and water meet,
Where the waves grow sweet,
Doubt not, Reepicheep,
To find all you seek,
There is the utter east.