Actually, you said “Tron: Legacy was awesome because Joe Kosinski wrote (and directed it.)” While he directed it, he did not write it and so is only partially at fault for its failure. If he did have a hand in writing it, he was smart not to have taken the credit.
Had you seen “Tron,” you could have appreciated the advancements in technical filmmaking presented in “Tron: Legacy” that much more and still be disappointed in everything else as were many “Tron” fans.
There are some scenes that can be used as demo material in “Tron: Legacy” for sure. But, make guests sit through the whole thing and some will surely fall asleep while others may leave early.
Many enjoy movies that didn’t set records at the box office or have critics raving about them. But, without good reviews from critics and audiences alike to help sell tickets, big sequels to big movies don’t get made right away. It took fifteen years for “Tron: Ares” to make it to the screen. If this one fails, expect another long wait for the next one if it comes at all.