That's true if you're optimizing for start-up success. The odds of a startup succeeding are pretty low and mostly tech is not the cause of failures though. When people learn a new stack for a startup they're optimizing for the startup failing, so they can still derive some value out of the failure.

This just comes down to a napkin calculation of expected value of building a startup given P(success). If your startup is looking like a real business out of the gate, using the simple stack you know is the way to go, and if it's more of a hobby project that you'd like to monetize eventually, learn something new.