Peak Outlook was 2016, right before the 365 mess.
I heard excel guys say peak Excel was 2010. Where there any genuinely useful features Outlook 2016 had over 2010?
Just off the top of my head:
IFNA, FORMULATEXT, DAYS, CONCAT, IFS, SWITCH, XLOOKUP/XMATCH, FILTER, UNIQUE, LET, TEXTBEFORE/TEXTAFTER, LAMBDA, et al.
But my favorite improvement is the "don't intentionally corrupt CSVs" options found in Settings -> Data -> Automatic Data Conversion (hint: Disable everything). Only took them 30-years to add that. Absolutely absurd these are enabled by default still.
Excel is one of Microsoft's best pieces of software and one of the very few they haven't turned into slop YET. Still don't understand why we don't have local-only Python to replace VBA at all license levels (i.e. non-cloud).