The flip side is that they don’t really play well with devices outside of the Apple ecosystem.
Personally, it’s something I have come to terms with long ago, when I made a conscious decision to embrace the Apple ecosystem in its entirety. Call it a deal with the devil or whatever you wish. Currently, everything still works great for me, and it saves me the hassle of having to consider competing alternatives outside the ecosystem.
Either go all in, or not at all.
But isn't the HomePod somewhat different? There is no disadvantage with regard to app availability when it comes to using iOS. In fact, one important advantage is that if you are part of the Apple ecosystem, you have access to all the apps you need, usually first, plus the developers are 'encouraged' to make the apps of a higher quality if they want to get through the screening process. And on the flip side, Apple provides iTunes for iPhone users who prefer PCs.
There is no disadvantage to using macOS. I get the best of all worlds with macOS being Unix and being able to run Windows. And again, Apple provides iCloud and iWorks services and Safari for PC users.
Many of the apps I have on my Apple TV are duplicated on my 'smart' Android TV, yet I use the Apple TV because the apps and UI are better. Same with my Beats X and use with PCs. Almost everything I use is cross platform, also on Windows and Android, yet the Apple ecosystem means I'll have a better experience.
With Apple Pay being an issue, I can easily understand why Apple doesn't make the Apple Watch work with Android.
TVs are the hub for all attached devices, so there is no real disadvantage to Android devices not being able to stream to the Apple TV. Just attach an Android compatible device to the hub (TV).
But the HomePod seems to take it a step farther. By not having an audio jack, it doesn't work with many existing audio systems. I can't connect a console to the HomePod to experience what gaming is like using it's technology. I haven't seen a reason yet how not having the audio jack is advantageous to Apple Music users like myself. I do see many disadvantages.