DLC is an absolutely fine concept when priced right and conservative Nintendo exclusive gamers will come to understand and appreciate this if Nintendo doesn't screw over their customers. $15 for 108 holes across six "courses" alongside new characters sounds fine to me. Less fine if (when) the price is hiked locally on my end of the world. But affordable nonetheless, with what sounds like a lot of content.
As Valve has argued many games are better suited to "services" instead of isolated products. Games like Mario Golf perfectly fit this, evolving in available content for the end user instead of locked to content with a single release, the only alternative to release entirely new bulk versions of the games. Content evolution from a single product instead of endless sequels. The balance that must be struck is content in the initial release with affordability and perceived value of upgrades/expansion/DLC. But it can and, under the right leadership, should be done.
For example, much like Mario Golf give me a Mario Kart that has me playing new tracks with new characters, with my friends locally and online, 12+ months after release. Keep me coming back. Keep evolving the product.