Why can't I control my HomePod on its own anymore?

I've had my HomePod mini for almost a year now and since the update to iOS 15, macOS Monterey, and iPadOS 15, I can't control my HomePod from my phone like I could before. Back on iOS 14, I could go to control center, hold down on the media player in the top right, and then below the iPhone media player you could press "control other speakers", which would let you independently control HomePod or an Apple TV and so on. Since the update, that button is no longer there, and I can't stream to my HomePod separately from my phones audio. What I mean by that is, before the update I could stream a song to my HomePod and then watch a YouTube video on my phone without the HomePod being interrupted, but now if I'm streaming something to HomePod and an alternate audio source starts playing on my phone, the sound comes through the HomePod. Is this an issue on my end, or did Apple really get rid of the feature? Similarly, you used to be able to play a song from your iPhone to the HomePod, and then take the song back to your iPhone, and if you tapped play on the HomePod it would continue playing the song as if it was never moved to the phone, but now it just plays whatever was playing before the phone connected. That sounds a bit confusing, so I'll give an example. If I asked HomePod to play music and music started playing, I could then play a podcast on my phone and stream that to my HomePod. That would interrupt the music from the HomePod and play the podcast. I then could switch the podcast back to my phone and walk away. If I came back an hour later and tapped play on the HomePod (without even using my phone) the HomePod would continue the podcast from where I left off earlier when I swapped to my phone. Had I done this after updating to iOS 15, the HomePod would go back to playing the music that was playing before the podcast. This may not sound annoying, and somewhat makes sense, but oftentimes when you're streaming something to a HomePod from your iPhone and then you pause the media from your phone for say 5 minutes, the phone disconnects from the HomePod. This means when you go press play on the HomePod, it plays whatever was playing before you connected, so you have to reconnect all over again.