I help people all the time when they get stuck and still give them offers. But it depends on how you get stuck. If you're struggling in refactoring from O(n^2) to O(n) but are able to get back on track after we talk through some ideas then no biggie. If you get stuck with the concept of iterating through a list then there's probably not going to be an offer extended.
I don't know about entirely stuck, but I've definitely spent a long time in the weeds on questions, writing code on the whiteboard that was clearly sub-suboptimal. I've still gotten offers. It's all about managing the interview, communicating, asking for a hint or two. Not guaranteed, but definitely possible.
I just feel like I've been on a lot of unicorn hunt interviews recently (casually looking at interesting opportunities, currently pretty happily employed)
Actually, in my experience you might as well walk out the door then and stop wasting everyones time. Has anyone ever experienced something different?