How depressing is it for us in the US that the Indian tax code is simple enough that someone can "show HN" a tax calculator.
Only because India's tax base isn't as elaborate as the US tax base currently. Gradually this will change, countries like India are growing and the government needs a lot of tax to build infrastructure and other stuff. I think in the next few decades Indian tax system would equally if not more complicated than the US tax system.
I fail to see why complexity is a necessary result of increasing tax revenues. Most of the complexity seems to come from policy initiatives and successful lobbying of special interest groups .. both of which may be considered to be misguided.