I used to work in an insurance company on an actuarial pricing team where the preferred tool was Excel (the modelling was pretty simple). Needless to say, I became very accustomed to and adept with using Excel. We definitely pushed the limits... but what was nice was being able to grab 600K records (maybe 20 cols) from a DB, throw it in Excel and get some results in a matter of minutes. You might have to wait a few seconds based on what you were trying to do, but Excel could handle it.
At home I run Linux... where there is no Excel, so I use LibreOffice instead. Just a few days ago I was poking around the Himalayan Database[1] and one of the tables has about 50K records. LibreOffice absolutely chokes when I try to do any filtering or calculations. As well, the pivot tables in Excel are in a totally different league than LibreOffice in terms performance and flexibility. It's unfortunate because I try to support OSS as much as possible... but LibreOffice is just so painful.
You could argue that I'm using the wrong tool for the job. Ultimately, I do throw it in SQLite or Pandas, but Excel is just so nice for ad hocs if it fits in memory.