I agree 100% that Marvel editorial really needs to tighten up...
There are several factors leading to the problems in Marvel Comics.
First, the quality of writing and artwork dramatically declined. Some of that has to do with editorial control and some of it has to do with Marvel hiring writers and editors with little or no experience in Marvel Comics. Many, in fact, appear to have little or no knowledge of the characters in question. So, you have stories which ignore prior continuity or haphazardly retcon prior history. Or, worse, repeat prior history.
For example, in Iron Man, they completely changed the main character, Tony Stark, to be an adopted son of Howard and Maria Stark for no real good reason. They introduced a new character, his “real mom” who is a completely useless character.
Second, Marvel is revamped many mainstream the characters to appeal to diversity, even if the new characters make little or no sense.
Again, with Iron Man (my favorite character) was replaced with a teenage black girl named Riri Williams. Keep in mind that Tony Stark went to war with the US government to keep his technology secret (look up Armor Wars). Yet, now, we are supposed to believe that he’d just turn over his tech to a teenage girl who he barely knows?
Third, the constant annual super events which requires readers to buy an enormous number of comics to keep up with the event. And, each event almost seems to have no impact on the Marvel Universe. The comics seem to lurch from crisis to crisis without any time to develop characters or have interesting stories play out.
Fourth, and related, the constant special covers and editions that no one wants.
Fifth, the constant reboots of characters that have failed. Captain Marvel doesn’t sell, so they’ll just reboot it. Or America Chavez fails so they release a new series. If the fans don’t want to buy the comic, stop making it.
Sixth, Marvel writers and editors expressing disdain or, even hatred, towards fans. I have literally been told that I’m a racist because I said that I’m skeptical of the Riri Williams character. The current writer of Iron Man, Dan Slott, has blocked me on Twitter and I have no idea why, but presumably because I follow Richard Meyer on Twitter.
TL;DR Marvel isn’t giving the fans what they want and expresses disdain for the fans to express their displeasure.