Frankly I think you're being optimistic/pessimistic (depending on your point of view). A person can be a "decent coder" by very reasonable definitions of the term and still not realize that Excel can't handle this particular volume of data.
I understood (different source; not sure what the true picture is) that the problem was with storing each record in a column. There is a limit of 16,000-odd columns. This would, as you say, not be a problem with Excel as such, but with the user(s) not being aware of the limitations (which is still the case in your scenario). I wonder how much the general problem has to do with mistrust of 'experts' so, hey, I can do this myself in a spreadsheet. (Or maybe it was just a decision on-the-fly in a fast moving situation)
This is the test and trace system for the worst pandemic this country has ever faced, six months in. I’m sorry Excel spreadsheets won’t cut it.
This is a management failure. PHE has capable coders. And if not, they could hire some.
The NHSX team has managed to write the dang COVID-19 app twice. Once not using the Apple/Google contact API (because management) and a second time properly. It’s all open source and it looks pretty decent.
As an aside on the Covid-19 app - it is open sourced in the "occasionally throw some code over the wall" kind of way - eg it looks like the github was last updated on 24 September vs the app which has more recent updates. It's not clear they open sourced everything needed to actually build the app either looking through the issues.
This is very very far from the only project doing that but disappointing nonetheless given the amount of public money which was spent on it.
