> I have never in my life worked with a database table that had 700 columns

Main table at work is about 600, though I suspect only 300-400 are actively used these days. A lot come from name and address fields, we have about 10 sets of those in the main table, and around 14 fields per.

Back when this was created some 20+ years ago it was faster and easier to have it all in one row rather than to do 20+ joins.

We probably would segment it a bit more if we did it from scratch, but only some.