A compiler with a good type system catches a mistake instantly instead of at runtime.

The difference in time it saves the dev can be anywhere from a few seconds to minutes per mistake.

Multiplied by hundreds of mistakes, it makes a huge difference. And that's not even getting into the advantages of better autocomplete for external libraries.

As someone who has written many thousands of lines of PHP, JS, TS, C#, Java, and Python, I now find it baffling that someone would start a project in 2021 without a great type system as a safety net.

The difference is massive. Computers are many orders of magnitude better at this kind of thing than humans, especially in a large application where changing the shape of a single data structure can have cascading effects throughout the entire code base; you simply will not catch things a typechecker will.