All the most profitable companies I've ever worked for, which also have had the smartest engineers I've worked with, would take longer than three weeks to build an Excel sheet import system. An engineer thinking it can be done correctly in three weeks, without bothering to know all the requirements, would be a red flag for all except the most junior of positions.

A junior engineer thinks speed is the most important metric.

In case it helps you to see OPs point, please contact this person for a spreadsheet to import.

https://news.ycombinator.com/item?id=18608294

It needs half a terabyte of RAM to open.

I remember all of the "I could write Twitter in a weekend" posts on blog years ago. Your comment reminded me of that, sadly.

What if importing an excel sheet actually means importing an excel sheet, formulas and all, instead of a CSV? Commenting on a hypothetical estimate on a hypothetical story isn't adding much value...