It works fine if the user is ok with the features from 2003. E.g. Excel 2003 is limited to smaller spreadsheets of 65536 rows by 256 columns but Excel 2007+ can handle larger worksheets of 1048576 rows by 16384 cols.

I also recently used Excel's new LAMBDA() function which was introduced 2020. In earlier versions, it required writing a VBA UDF to accomplish the same task of assigning a temp variable with a ephemeral value to calculate on intermediate values. VBA is a workaround but LAMBDA() is nicer to use because Excel will throw up scary security warnings whenever the xls file containing VBA macros is opened.

I might be able to get by with Word 2003 more than Excel 2003.