All in all, there IS new content. We cannot ignore the fact new Quests and content IS being added to the game, meaning they are not just remaking the old stuff, which I assume is being re-drawn and re-animated from scratch. I am a writer myself, and I understand how such a process can work. When you rewrite a story with the aim to improve it, you must always be careful about the little things. Sure, it is taking a long time, but if the issues were just the scenes? This game would have been out again in full LAST YEAR.
They are writing new content for the new quests, which they need to fit into the timeline and stuff. Not to mention they might want to avoid having to modify the Main Story too much, hence why it likely takes time to make sure no 'small details' fall through cracks.
In my personal opinion, I think DC is dealing with burnout more than anything. Plus, Debbie's questline, along with Jennie's and maybe even Mia's, are the most inter-connected with the Main Story that I can think of! I am sure that once we get past the Main Story content, and most technical stuff they are most definitely working on behind the scenes we do not understand, that things will pick up regarding the speed of returning content.
DC, if you ever see this post, gimme a reply with your personal opinion. I want to believe in you, but time might just wear me down, too.