Some are working on cool things, but the founder who has a PhD in that topic will be doing the interesting work and they are hiring for infra or interface.
One company was a great match for my skill set but the equity was so low for early hires. I get that 1% can be huge for a FB scale exit, but 180k and 1% is generally just a paycut. In this case the founders were undergrad dropouts and not SMEs. It just seems like a really inflexible ecosystem when you can't give 5%-10% to an early hire when they would be the SME and core engineer.