They really took the Ferengi and tossed them down the drain with that stuff....
That implies that they were ever interesting. At best, they served as a nice backdrop, a presence amongst many other alien races.
The Quark character was a good idea. The rest.. ugh. Ferengi "society" just wasn't interesting enough to explore.
Again, it's just what happens when there's too much TV to make. The new versions of the Klingons introduced in TNG were interesting enough, up to and including the civil war cliff-hanger (when Warf temporarily quits Starfleet to fight with his brother). After that... man, how many times did Warf get disowned by the empire? Jees.
Even the Borg got played out, IMO, after the Locutus thing. After Locutus, they decided to slowly remove everything that was cool about them. They start making them human, they introduce a beaurocratic hierarchy- that is just lazy, unimaginative science fiction writing. As awful as 7 of 9 was, you can blame Hugh for starting it all.
One of the many incrompehensible mistakes Voyager made was not dreaming up some new alien races worth exploring, like the original series did with Vulcans, TNG did with Klingons, and DS9 did with Begorans and Cardassians. They came with whatever-the-hell Nelix is, but unfortunately his race is represented by Nelix. Then they had Kazons, but they were just angry humans basically and quickly dropped.
Ironically, the one race they didn't beat into the ground is the Vulcans, because they weren't at the center of any of the new series' storylines.