The problem is basically always the same. They decide more or less broadly what should be in the update, then DC writes down what he plans and often makes a post on patreon. But that's before the actual, detailed content is written and before they potentially add stuff because they think it benefits the update.
I mean, it's nothing new that he's terrible at predicting how long updates will actually take. It usually goes well for the small ones with limited content, like Consuela or 0.18.5 for Jenny, but for the longer ones they are always somewhat off. I mean, that's why there's never a set date and why he never actually commits to anything.
Once you know it, you can easily live with it and just factor it in. This whole creative and flexible workflow with lots of influence from picarto etc. is certainly nice to have but it has downsides, too.
Edit: It simply feels like they try to make it too "good" at times. If there's a decision to make and you too often go for the "takes more time but really helps the game" option, stuff adds up. Sometimes I'd wish they'd just return to simpler writing, simpler quests, less wallpaperscenes, less pregnancy, etc. because all of that just takes a lot of time which many people won't appreciate. Then again, I'm personally not in a hurry and I don't really care whether it takes a year or two longer or not.