Instructional material that led to rave reviews and amazing student outcomes the years before now results in similar reviews like “lost a lot of respect for the Math department after taking this course.”
The main complaint is "Why won’t anyone teach me XXX": "it seems like the instructor is expecting us to learn the material ourselves".
Sorry to say, but for many STEM topics that's the only way. You need to struggle, do, and solve the problem. And not only there: you won't learn figure skating / cycling / playing an instrument by watching a lecture (or video) on it. You have to actively do it. The instructor can lead you to the water but can't force you to drink. Just staring at the water and complaining does not help.
I wonder what these students will then feel like in their first job. You hire engineers because you have a problem that needs solving. This kind of graduate on the other hand expects that someone solves the problem for them and feeds the solution in small packets.
Also, of course, it's interesting to wonder why this is happening now and if it will go away. The connection to the pandemic seems clear, but how exactly?