Excel sheets aren't very maintainable. You get a big grid, plus named ranges. There aren't good tools for generalisation or abstraction, so big sheets have all the usual problems of bad software: hard to understand, hard to change, full of inconsistencies, etc. There are also no good options for source control, modular reuse, etc.

I work on a desk which has a lot of vital calculations in Excel spreadsheets. They work, and we make money, but it takes a lot of human effort (expensive trader effort!) to keep them working properly. If we want to scale up - more people, more products, etc - we need to move more and more of those calculations into software.

Improvements to or replacements for the spreadsheet as tools for non-programmers would certainly be helpful. But better tools and techniques for programmers to port functionality from spreadsheets to 'real' software would also be helpful.