I get both perspectives, but as someone who doesn't have the time to play through the big releases on launch, I do appreciate them erring on the side of tiptoeing around spoilers. Even now, I find myself scrambling to find the pause button when they start to get into details about last year's big hits that I'm still working through. That said, when I *have* beaten a game, I'm the exact same - I want to hear their thoughts about *this* big twist or *that* cool scene or whatever. I think more frequent spoiler casts are a good middle ground but I don't know how much time they can dedicate to doing that from a production standpoint.
EDIT: I'd add that spoiler casts make it easier to find and go back to hear their thoughts once I *have* caught up on the big releases.