To make it bluntly.
It has terrible pacing and character development. Using a significant moment in history like the French Revolution, which would require heavy elbow-grease to avoid deviation from the actual story itself. However, commits to the latter anyway. Not only watering down the expectations of the story, but bringing down the emotion of urgency and desperation during the French Revolution.
Some people complaining about "wokeness", which is strange because it was a time of "Liberté, Egalité, Fraternité". A "woke" slogan.
A reason why people might be blaming "wokeness" for the travesty known as 'Castlevania Nocturne', would probably come down to poor writing and a feeling of exclusion from Richter who is portrayed as the main character. It is plausible that it was not intentional, but incompetently accidental.
Again. The show tried to tie the story with the setting of the Revolution by focusing on the injustices of autocrats and slave owners. Specifically, on the support character. As I stated before, the Revolution cannot be simply tied to the characters by having one of the support characters relate to the injustices that the Revolution fought against.
To conclude, poor decision making, mixed with muddy writing can cause this sequel to fall short of its predecessor.