When you don’t have static typing, what you really miss the most is the ability to make data-type related assertions and to do so at compile time.   But there are many ways to implement that, which do not unduly restrict your flexibility in handling data at run time.

At run time, the notion that “a piece of data is a self-describing object” really is convenient, and it really is efficient.   Sometimes much more convenient than the static-typing of the days of yore, when computers were much slower and smaller and “you did what you had to do in the very-tiny shoebox that you had.”