So here's my take. I'm sure it will ruffle feathers...
For me, the Kessel Run exemplifies the problem I had with this, which I'll get to in a minute.
I found the movie to be... fine.
And that's a problem. I don't want a Star Wars movie to be fine. I want it to excite me, not just visually, but on a deeper level. I'll even take polarizing over fine.
I mean, the movie was well made. The action was good. The visuals were solid. The actors served the material well. I don't feel as though I wasted my time watching this. On the other hand, I don't really see myself caring one way or the other if I ever see it again, which is something I have not yet experienced with a Star Wars film (including the Prequels). In fact, I came out of the theater with a strange feeling of sadness.
After thinking about it for a little while, I realized where that vague sense of sadness was coming from. This movie was answering questions I wasn't asking. No... more than that, this movie answers questions I specifically didn't want answered.
And that brings us to the Kessel Run.
One of the best things about Han Solo (prior to this film) was this sense of him being an unreliable narrator. There was this sense that everyone just assumed the Kessel Run story might, in fact, be bull****. Han is like that friend who has had a pretty interesting life, but who also has to make their stories just slightly better than yours -- even if that means embellishing. If you say you ran the Kessel Run in 14 parsecs, Han has to say "yeah, but I did it in 12."
Not knowing what about him was real and what was just a tall tale is what made his character great. You just didn't know if you could trust him, so that when he does come through as a hero, it actually means something.
I was already skeptical of this film because there just wasn't any legitimate way for it to put our main characters in any real physical jeopardy. Also, there was only so much emotional trauma this film could realistically put the characters through because we've already seen how they turn out. However, I could have forgiven that had the film stuck to material we didn't already know, because those were the parts of the film I found most interesting. The heist was fun and inventive. But I just couldn't be emotionally invested in the Kessel Run, or any other of the scenes we already knew were coming (Han and Chewie meeting, the card game, etc.), and that's not a good place to be in for the key elements and climax of the film.