Their biggest challenge here is that they're still really not churning out content quick enough, and I'm not sure they'll ever be able to without partnering with some other companies or services. The great thing about Netflix/Hulu is that when you're done with their exclusive shows, you can fall back on other well-known movies and shows, and continue getting value out of your subscription. A streaming service that ONLY has entirely new, exclusive/original shows, which you've likely never heard of, outside of maybe Ted Lasso and The Morning Show, is a really tough sell to the average person.
That being said, I think all of the shows I've watched on it are insanely high quality. The $5/mo. asking price is really reasonable, but also the lack of content lends itself to be easily cancelable when you're done watching what you want (likely why they only roll out one new episode per week for new seasons). In a few years it could be really great, and I think as such, Apple is treating it as a long-term investment. It's a nice supplemental service to have currently, but likely not anyones main go-to service.