It's important to realize that these tools just didn't exist 7-10 years ago when companies like Instagram and Dropbox were getting started.
Though type inference has been around in so-called "academic" languages for decades, it hit a tipping point in the last 10 years, to the point that every major dynamic language has static type checkers or dialects (like Typescript) that support static checking. Meanwhile, even traditional statically typed languages are growing stronger type checkers.
Though type inference has been around in so-called "academic" languages for decades, it hit a tipping point in the last 10 years, to the point that every major dynamic language has static type checkers or dialects (like Typescript) that support static checking. Meanwhile, even traditional statically typed languages are growing stronger type checkers.