The "just be happy they made (product) at all" mentality isn't really a great one to have. As a paying customer who dropped 60 bucks or whatever your equivalent is on the game, you should be able to be satisfied with what you got, and if you aren't, you're well within your rights to voice that opinion. If companies keep making subpar products and no one criticizes them, well, they're most likely going to keep making subpar products. If you enjoyed a game or really any piece of media, great! You had a good time and got your money's worth. But that doesn't mean people who didn't like it are wrong or shouldn't be allowed to criticize it just because it exists. Nintendo didn't give anyone a gift by making Battle League - they made a product that you had to spend your money on. (Heck, even if you didn't buy the game, you should be allowed to criticize it and explain why you didn't think it was worth spending money on.)
Honestly, it is pretty embarrassing on Nintendo's part that they're pumping out sports games that either struggle to reach around the same amount of content that games 15-20 years old had, or even worse, fall short of that. But they're still doing it, so clearly the sales numbers are high enough that they think this is a viable strategy. And going back to them doing around the same amount of content as old games, I wouldn't get caught up in defending Nintendo just because they did "enough". This isn't some indie studio, it's one of the most successful video game companies in the world, they can and should be able to do more than what they were doing decades ago on inferior hardware. New games should build on old ones instead of making you cross your fingers that you might get as much content out of it as the original. (It's similar to why I don't like the argument meant to defend things like *cough cough* Sticker Star of "well, it's not anywhere as good as what they've done before, but it's fine if you look at it by itself". Don't settle for that! You're getting an inferior product from a team that has clearly demonstrated they can do better!)