It was surprising to me to learn that exactly zero of the profits they rake in from their player base goes towards providing any server architecture whatsoever for developers on the platforms to use.
To me this was always the most insane part. Like I would pay for e.g. Xbox Live if it is stable, free of cheaters, etc. but they will not get me to pay for peer-to-peer how it's with Nintendo's own games. :O
It's not open source and not ready yet, but seems interesting. https://walt.is/