Because Ollie is a cock. Even when you go back to when their relationship wasn't a shipwreck, it was a shipwreck.
Thirty-something hitting on a nineteen year old: fail.
Ollie goes on a gaycation with Hal without telling Dinah: fail.
Ollie loses shit when Roy has drug problem, dumps him on Dinah: fail.
And those were the golden years. Post-Grell it only goes down hill. Green Arrow's been a miserable stump of a human being for twenty years, and the best excuse his fans can come up with is, "It's the writers."
To answer your question, the "awkward marriage phase" is due to Black Canary having spent the better part of ten years (1994~2004) evolving into a wholly different character, where as Green Arrow is still (on purpose) the same guy he was in the 70's and 80's.