When I open .csv files Excel does exactly nothing to them. Perhaps that's because I open them as .csv rather than importing them into Excel? I then save them as .csv without making any changes. If I want to import data into an Excel file I usually copy and paste it into places where I've already set up the formatting. So dates get turned into dates in a way that I control. It's 20 years since I was a heavy Excel user, so I've forgotten loads of it now.
It does suffer from being a program designed to do financial stuff - that's morphed into a Swiss Army Knife - which then gets abused for jobs a chainsaw would do better. Yes, I did once use Excel to print a crude poster for a seminar on the Water Regulations, who's asking?