As hard as it is to remember, there were buzzy startups in Silicon Valley before the tech world became solely fixated on artificial intelligence. By the time the Covid-era tech boom crested in 2021, well over 1,000 venture capital-backed startups had reached valuations above $1 billion, including fake meat purveyor Impossible Foods Inc., home maintenance marketplace Thumbtack and online-class platform MasterClass. Then came a squeeze sparked by rising interest rates, a slowing initial public off...