I'm pretty good with Excel, my main tool at the job for over 20 years. I understand how he did it, but it's just really humbling...
I still think quality of what you do with Excel (idea) is more important than how you do it (skill).
First of all they had an invoicing system in Excel, that pulled in data using VBS, into Excel templates, and at the press of a button in the UI generated invoices from these templates.
And the craziest part was their server inventory system made in Excel, where they had drawn all the rack cabinets, you could click on each, to drill down and show all the servers in that rack. Also a ton of VBS, you could even get monitoring status of each rack.
Excel has been OP for a long time, long before its Python capabilities.