Over the last decades, I hardly needed to upgrade Excel. For a very long time I stayed at Excel 2003, as the ribbon interface introduced with Office 2007 (version 12) was horrible (it still is, especially since 19:10 monitors are gone and the ribbon takes too much vertical screen estate).
After that, I needed newer features so I upgraded to Excel 2013 (version 15) mainly because it ditched Multiple-document interface (MDI) and I like SDI over MDI a lot, and Office 2013 was largely compatible with Office for Mac 2011 (version 14).
Mostly recovered from my cancer treatments, I noticed that MacOS ditched 32-bit support in MacOS 11 Big Sur, which meant I could not use Office 2011 any more (it was 32-bit x86 only) so in 2022 I upgraded all my office installations to Office 2021 (up in the version 16.* range as starting with Office 2016 the major version number stayed 16.minor).
I might actually upgrade to Office 2024 (version 16.many) soon despite the major version 16, finally Excel has started sped up new development of new functions and features, of which the ones below are very interesting: they will make my largest spreadsheets a lot simpler and therefore easier to maintain:
The Wiert Corner - irregular stream of stuff 