I just hit $750k in total assets, and $500k in investments.
I was in a scenario in 2017 where I had enough cash on hand to pay my mortgage off. I chose to pay it off instead of invest it. Was it the right decision mathematically? Perhaps. Perhaps not. Time will tell, but my personal situation was atypical and it's probably much closer to a wash than your typical scenario. I'm in the hold-your-mortgage camp despite having paid mine off due to my unique circumstances.