Twice frequently had 3+ comebacks in a year. For example, 2018 had: What Is Love? (mini), Summer Nights (repackage of What Is Love, with new title track Dance the Night Away and another new song), Yes or Yes (mini), Year of Yes (repackage of Yes or Yes, with new title Best Thing I Ever Did), AND ALSO, the Japanese album BDZ (which itself had three singles promoting it in 2018 - Candy Pop, Brand New Girl and BDZ - all of which had MVs and were performed on Japanese music shows - along with the OST track I Want You Back which also got a music video). Throughout this, title tracks would be performed between two-four weeks on music shows.
While they're an extreme case, 3 releases in a year wasn't uncommon. In 2017, Red Velvet released Rookie (mini), Red Summer (mini) and Perfect Velvet (full album). For example.
If Nmixx were like Twice, it would be reasonable to expect another comeback around now tbh!
But Nmixx has always:
1. Released far fewer songs than any other JYPE group since Miss A.
2. Had a music show performance schedule shorter than, at least, HYBE groups. I think they only do two weeks now?
Which is why Le Sserafim were still promoting while Nmixx has finished up.
I think there's two reasons for this. One is their division, Squ4d. Squ4d is supposed to be independently run by Lee Ji-Young, who was Twice's creative director between Page Two and Feel Special. It was given its name and branding specifically because it had greater autonomy from JYPE proper. I think Ji-Young has the internal clout to leave money on the table because she basically saved the company. For example, my feeling last year was that SKZ' Hop and Twice's Strategy were rushed releases to pad out JYPE's final quarter because their year-on-year revenue was about to show a significant decline. Itzy also put out Gold in that quarter. Nmixx didn't put put anything out. I think because Lee Ji-Young can just say no.
But secondly, Twice famously burned out from all the work they did, and I think there's an understanding that going slower is more beneficial both for health and, perhaps, long-term financial prospects.
About that last point: Girlgroups in the past had to strike while the iron was hot and release quick because they had a five year window of profitability. With the opening of the international market, this isn't true anymore. So I think there's less of a rush across all companies. For example, Ive only had one Korean release last year, despite being the arguably the highest-selling girlgroup. In the past ten years, you wouldn't expect a super successful group only in their third year to only do one release.