Every operational workbook is a record of something the software stack could not answer. The overtime tracker exists because the scheduler and the timekeeping system disagree. The coverage grid exists because nothing compares published hours to expected demand. The site exception list exists because there is no place where an exception lives.
That makes the workbook a good specification and a bad system. It states precisely what is missing, in the operator's own language, and it fails in the specific ways that hand-maintained data fails: it goes stale between updates, it acquires undocumented rules, and it stops when its author is on vacation.
The useful move is to read the workbook before replacing it. If the replacement cannot answer the questions the spreadsheet was built to answer, the spreadsheet will survive the project, and now there are two systems.