Current CSU Lecturer here, working for one of our largest campuses. Since I started 10 years ago, my department (CS) has seen more than double the amount of enrollment. Projections for us are to double again in the next 4 years or so.

The decline in student population might be a thing system-wide, but not for certain areas like STEM.

Edit: Also, we have lost quite a few faculty due to our poor pay, which makes our overall class sizes huge. When I started, class size was capped at 35. Now I have two lecture-hall size classes at ~100 students per class.