>>16205156I use it every fucking day for my hobbies, and it's extremely useful to me. Grinding the language has been one of the best choices of my life once I decided to consume Japanese media and entertainment.
You can argue that it doesn't really open up any realistic job opportunities, but that doesn't mean it's not useful if it improves the experience you have with what you enjoy.
People learn very specific jargon that can rarely be applied to their occupation if their hobbies are cars, trains, and music. They learn very specific reflexes that can rarely be applied if their hobbies are video games or sportsball. But they learn all of those because it enriches their time spent with their hobby
Knowing Japanese will enrich your time watching Japanese vtubers and cartoons, reading manga/WN/LN/VNs, and browsing twitter/5ch.