> but my data is dynamic

In my experience, most dynamically types code makes assumptions about structure that may not hold later (better have tests!) and when it breaks some kind of validation is needed anyway to select between the correct version of the different dynamic options. In static languages this is simply typically done sooner, since the type system requires it to parse the data. (Or it’s in variants that are accessed without checking that the accesses are valid, sigh)

The type system depends on the kind of data you want to keep around in your columns, which could be a mix of types, and it could be all strings and NaNs, for example. This is common with DataFrames. There's a huge number of possible combinations of data you could be reading in that you need to clean up, reshape and then analyze. And you might be making decisions on how to do that in the middle of your wrangling. It's just like what you can put in Excel or a CSV.

I know. I've been doing this sort of thing for most of my adult life.