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).
Reminds me of the old joke about it: How is Microsoft Excel like an Incel? Both think everything is a date.
It still butchers long strings of digits if they are more than around 12 and less than around 15 digits long, its very annoying still.
Also textjoin and textsplit and the whole spill functionality.