There is no competitor, proprietary or open, that comes close to Excel. It's been relentlessly,
extensively polished for years and years, and keeps gaining new features every year.
And this sticking to the spreadsheet concept, which is very limiting.
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Contrast for example Tableau -- it's a great idea and generated a lot of enthusiasm for a while, but never quite took off as an office package one needs to have. The normal awkwardness of its first versions is still there; they don't have the deep <whatever> that the Excel team has.
Tableau is great, but it has a much narrower use case: given one or more tables of data, generate graphs for presentation or for exploring the dataset.
In comparison, Excel can do that too (just worse), but it can also solve equations, do your company's bookkeeping, and pretty much every other task that relies mostly on numbers.
I would argue Open/LibreOffice Calc comes fairly close to Excel if you ignore the worse user interface (which is fair in the original assertion that it's "mostly polish and small incremental improvements")
And this sticking to the spreadsheet concept, which is very limiting.
---
Contrast for example Tableau -- it's a great idea and generated a lot of enthusiasm for a while, but never quite took off as an office package one needs to have. The normal awkwardness of its first versions is still there; they don't have the deep <whatever> that the Excel team has.