The worst I saw was a network hardware and service provider maintaining all their products and services in Excel spreadsheets per contract. Each of those had all the relevant information, the list of products, when they were due for renewal, service, or replacement, and the agreed-upon rates.

I was there to get them off that system doing ETL to Oracle, which was only the first part of getting it to SAP. It was interesting to see all the diverse and creative ways that the structure and formatting of these contract spreadsheets diverged. The worst was encoding crucial information in colors or other styles of the cells. That required automation from both outside and inside the spreadsheet, as well as develop a full library of heuristics to determine which strategy to use to visually parse the sheets. Looking back, I don't even know how this wasn't a multi-year project and it got done (at least the pre-SAP parts) on-time. Even then, half the work was still on the Oracle side once the data was there but barely normalized (what's less than 0NF?).

There are still opportunities for us SWEs even with the advent of chatGPT. Heck, lots of businesses are just an IG page + Google Sheets.

And or access databases.

+7 years ago, heard JPM had +20k of those on their networks. I just shiver thinking about that.