Depends on the nature of your oncall. If your oncall is just following documented restart procedures when your app gets stuck, you won't learn much. If your oncall involves deep investigation into your system and how it interacts with other components (services, databases) etc you'll learn a lot.

per some sibling comments though, years of experience != veteran, to be clear. There's certainly people who have been working for 10+ years, sometimes even at the same company, and don't really understand what they're working on.