The overall lack of knowledge in this thread of how revenue and fund distribution works is really killing the argument against Nintendo charging for online play.
The reality is that we, as consumers, can't expect things for free. I mean, sure, you can, I guess, but an adult living in the real world knows that things cost money. This very site staying up and running with all of its features is a direct result of ad revenue and premium subscribers. Do I enjoy paying a yearly fee? Not necessarily, but it helps keep the site I like in business, therefore I pay.
Nintendo's online functionality, from its first party games' servers to their friends and lobby systems are years behind their competition, and it's not a coincidence that their competition makes users pay for their services. It's not a coincidence that PSN also used to suck, with no party chat, cloud saves or even online backups of your trophies (not to mention their huge data breach and multiple-day-long outages) until they started charging for PS+. There are limits to what a company can do for free, and Nintendo's out-of-date online functionality for the Wii and Wii U were a direct result of those limits.
Anyone, as a consumer, has every right to say that he/she doesn't like the idea of paying for playing online. That's their right, and they can protest with their wallets by not paying for it. But saying something like "Nintendo has enough money, they should just give us upgrades for free" is a baseless argument that sounds like something an elementary schooler would say. Nintendo's offering you a service. It's up to you to decide if it is or isn't worth the price their asking. No one's holding a gun to your head and forcing you to shell out twenty dollars a year to play your $60 game on your $300 console.