No it means those not raging on the forums are happily using Fitness + without issue.
We'll never know. Apple will know. We'll see what they do.
No idea what is going on with some, but I have completed 6 sessions totaling 2+ hours without any issue. On iPad and on ATV 4th Gen. Cheers.
Yeah, it's a great product if you have an Apple TV, 4th gen or later. And, many workouts (e.g. treadmill, bike) would be great on an iPad. I'm happy you're enjoying it. I'm embarrassed to say that I did go out and buy the 3 year old model of Apple TV. I've done many more workouts than you and they were all fantastic.
Regarding the "no idea" part of your post, I can't answer that; I can only speak for myself. There are two parts to my answer.
Part 1 - Let's see if I can explain my workouts and those aspects that I find impossible with only an iPhone.
I do exclusively the Yoga, Hiit, Core, and Strength workouts. Those workouts have you lying down, sitting down, and standing up at various points. All of those workouts (especially the Yoga which I do the most of) demonstrate various adjustments as slight as small twists to the hands as you place them on the mat. They also have two other trainers in the background (hence much smaller) demonstrating alternate approaches for those with more enthusiasm or challenges.
For me to see all of this easily, my phone needs to be no more than about one foot in front of my face. I don't see any way to make that happen. An iPad would not make it that much easier. The one foot limitation might extend to three. The yoga routines I've tried had me moving smoothly to different parts of my 6 foot long mat.
There's a good chance that I'm just part of a fringe group. I if weren't, then I would expect more complaints on the internet at large.
Part 2 - The whole issue goes away if you have an Apple TV where you want to work out. I believe almost all complaints come from people who don't have that (or are making the case for the benefit of others). You are not in this camp because you have an Apple TV (probably just where you want it).
I believe the outrage comes from the conclusion some people reach, that Apple expects (or is pushing) its customers to buy an Apple TV to make up for this lack. Or, that Apple shares the view expressed by some on this thread, that the people who matter (the true enthusiasts) should already have an Apple TV.
I have not yet reached that conclusion. I still feel that it's either a bug, a temporary compromise they made to get the product out the door, or that there is a significant technical or legal challenge to make AirPlay work. I find it impossible to believe that they didn't consider the AirPlay issue when designing the product offering.
And, without a doubt, Apple support is clueless and we'll never get a straight answer from them.