This issue comes up from time to time with friends of mine.
I recall the days when artists like Kirby, Curt Swan, Dick Dillin, The Buscema Brothers, etc were doing at least two books simultaneously during any given year. And the books were always ON TIME for the most part.
Yeah. The system in those days were hard-driven with low wages. But works of these old guys are still standing the test of time.
I just see many of today's comic book artists extremely full of themselves, with no regard or caring for deadlines. These young cats today are straight-up LAZY in some cases. And you really have to blame the comic book companies, conventions, fans, etc. for fulling these dudes' heads with celebrity status.
I'm not saying that some artists aren't doing their best to give readers their best work possible. But all these late books were never a major issue over a decade ago.
If an artist/writer combo are doing a run on a series, I think companies should make sure they have a set number of issues ready to publish first, instead of waiting for catch-ups.