I think Apple Fitness+ is working quite nicely as an online service for sports. The integration of Apple Watch metrics is unrivaled and works great, the whole thing is very beginner friendly and the workouts are designed to gently engage the muscles, joints and tendons, thus minimizing the risk of overload and injuries. And being able to use it without the watch just on an iPhone makes it even more accessible.
The only thing I'm really missing out are workouts for advanced athletes. Of course, when performing dumbbell workouts you can just add additional weight, but in other disciplines like e.g. yoga this doesn't help a lot. Usually, the yoga workouts at Fitness+ consist mainly of beginner poses, with the option to perform one or two intermediate level poses in the longer workouts. Advanced or Expert poses are left out completely. But that's really not enough if you want to engage a little more - I'm not anywhere near being an expert yogi, but I use workouts in yoga apps or on youtube which consist mostly of more ambitious poses, and the sequences are a lot more demanding there. In Fitness+, I always have the impression to stay on the "eternal beginner level" - there are a few options to do a little more demanding work, similar to a gym course, but if you already reached a certain level which is not necessarily anywhere near competitive sports, but also not on the greenish side of beginners anymore, there is no real chance to grow.
There are so many workouts now, such a huge number of great exercises to choose from, with new ones added on a regular basis.
I think it would just be great to dedicate a few of the new ones to the advanced sportspeople.
Maybe in a separate section, where members could be warned that the content is only recommended for the experienced? This would minimize the risk for the beginners...
Combining the specific strengths of Fitness+ with a programme for well-advanced athletes would just be such a great opportunity, at least in my humble opinion.