From what I've seen,
Marvy Jack (responsible for only some furry and schoolgirl shit over a decade ago) has decent quality.
I've heard that Season 4 of NNT was rushed into production for less than a year, and after the considerable failure of Prisoners of the Sky.
Basically, they purportedly had next to no time or budget for 24 episodes, and very little help from Studio Deen (who were supposed to do some of the heavy lifting).
Season 5 apparently met a similar fate with time and budget, plus the pandemic happened.
This is only when it comes to 2D animation, though.
Grudge of Edinburgh is an
abomination.