Hi,
I am on 16.1.53.1594.
I am trying to load file with about 20K records and it takes almost an hour to load.
No constraints are enabled and no indexes are active.
Same file gets loaded in less than a minute in SQL Developer.
We were able to reproduce hour-long imports with your file. This is a bug and it will be fixed in version 16.2.
Until then, as a workaround, when importing data with dates from Excel files, make sure that Toad's date format in Options -> Data Grids -> Data matches the format in Excel, and then it will be fast.