So many great cases in this discussion.
To me, "Worst Era" implies a dark age of sorts, where sales and quality dipped. No buzz.
I feel the post-Giffen/pre Morrison era was the worst (1992-1996). There's a reason why Morrison RESTORED the Justice League. It was 100% dead as a title, franchise, and concept.
Even though Giffen/DeMatteis lost steam at the end, Dan Jurgens taking over didn't help. He's one of the most pedestrian, ordinary 1990s writer/artists, but his work isn't as consistent as that may imply. I'd rather have any 1980s in-house artist drawing to spec and any 1970s/80s middle of the road writer than Jurgens. Dan Vado and his rotating pencillers were worse! Instant 50 cent box trash.
Then came Zero Hour and Gxxxxx Jxxxs promised a return to basics. Well, I got tricked. Bad costume designs, horrible Guy Gardner stories, questionable roster, bad artwork, and unimportant storylines. Ugly, disappointing, skippable run.
And that's just the MAIN title. Through in Task Force (which started off fine but jumped the shark) and EXTREME JUSTICE, and ohhhhhhhhhh my goshhhhhhhhhhh.
I wasted so much money on this era!