It seems like you have the perception that top talent is easy to hire. In my experience that hasn't been true at big or small companies, and if a candidate is exceptional companies will go the extra mile to get them. And if we're talking about early stage startups the power dynamic is totally reversed - the senior candidate actually has a ton of negotiating power because a startup can't compete on salary with FAANG companies, and good candidates know it.

Good senior people are selective and want to know a lot about the companies they might be joining. If they didn't ask perceptive questions I'd think it was a red flag.

I mean seriously, a startup is trying to hire a senior engineer, is offering less base salary than Google, stock with an average value of nothing and they don't even want to answer the hard questions? How would they ever hire anyone good?

The only people I'd give a pass on not knowing asking good questions in an interview are interns or new grads.