I was at a uni with departmental IT and I certainly could do that, I knew the 3-4 IT people by name and I could just message them and get whoever was on campus

I was at a uni with departmental IT and I certainly could do that, I knew the 3-4 IT people by name and I could just message them and get whoever was on campus at the time to help me immediately if it was urgent. There are things better done by a central IT team like university level WiFi, but you can make that smaller and also have departmental teams for things where more agility is needed. If the people are competent it's really great. And yes 3-4 people only makes sense because it was a large department, but smaller departments with similar mandates, for example English/Literature and History, just have a shared departmental IT between them.