In other words, it's comparable to an early 90s PC. The fact that it can run a browser, complete with JS support, seems nearly unbelievable these days.
When I turn off my laptop on battery the next day it's dead because for some stupid reason we can't even get turning devices off right anymore.
That surprised me as I wondered just how much JS capabilities the browser has; then I realised that article was written in 2013, when Twitter was still relatively sane and not the bloated SPA it is today (yet the actual content being displayed is not much different from 10 years ago.)
The old-net kind of works on the DSi's browser, utilizing snapshots. But SSL issues today have also made the browser quite cumbersome.