I don't think the "dip in quality" from 1987-2007 has fully been debunked.
It's not just a matter of creative teams if JMS/ Romita Jr were telling better regarding stories prior to the reunion than after.
It's not a matter of different publishing standards/ eras if Ultimate Spider-Man was topping comics published at the same time.
As for the explanation for a perceived dip in quality from 2008-president, the explanation is simple: taste.
It was rushed because certain beats occurred pretty quickly.
One of the things that persuaded me that the marriage wasn't a wise move was my own feeling that between the marriage and One More Day, comics in which Peter and MJ weren't married/ together were better than those where they were married to one another.
If your argument is that the marriage was good for Spider-Man, the quality of stories in which MJ was believed dead or was separated from Peter does not appear to help.