I generally agree with this, except I would change "impossible" to "exceptionally hard." You're right that a lot of startups innovating on deep tech need to hire people who would earn $500k+ elsewhere, and that a typical startup can't afford that.
However, very exceptional founders can often raise unusually large rounds early on. I.e. some founders can raise a $10m or $20m "seed" round at inception, which allows them to afford to pay $500k salaries. It's the top 1% or 0.1% founders within their fields, but it is possible.
(Source: I'm a VC)