Your question is confusing. You ask Why doesn’t the App automatically focus to the room that is automatically playing. The you say..Apparently it is designed so that you always first have to go to ”Your System”, then select the room you want to play music in, and then you can start to play something. Three steps instead of one.  What do you mean by “ you always first have to go to ”Your System”, then select the room you want to play music in

If you are playing the same song in all rooms that means you have Grouped rooms together.  If you stop the music at some point and come back to the app later the “Now Playing” section will show Multiple Rooms that were previously grouped as in the picture below; unless you ungrouped them at which time the app will default to a single room.

If you are trying to play a different song in each room then continue reading….

On the home screen of the App the “Now Playing” section (at the bottom) will always show the last room selected. So in the example below the last room I selected was “Lounge”. I can continue playing the same music in that room by pressing play.

If I want to select another room to play different music I select the drop-down arrow as circled circled. This is also on the Home Screen. See next picture.

From this screen I’m going to select “Fireplace”. See next picture.
 

As you can see “Fireplace” is now appears in the “Now Playing” section. Now I can select any song I want from “Your Services” or Music Library stored on my NAS. This time I’m going to select “Apple Music” with songs by Aaliyah. See next picture

As you can see can see Aaliyah is shown in the “Now Playing” section in “Fireplace”.  See next picture.

Finally you can see that Lounge and Fireplace as well as other rooms are playing different music. 

To conclude it’s a simple process to play different music in multiple rooms. You just have to know how to navigate the app. However, if you feel that Plex offers a much simpler room selection process; then by all means continue. Enjoy your Sonos!

Someone at Sonos had a "really good idea" and now we live with it.

I tried numbering my Rooms and it helps a bit but they still get scrambled.

Reminds me of my Garmin sat-nav that will only display saved destinations ranked by distance from your current location. 

Gaaahhhh! ANY SINGLE ORDER no matter what would be less frustrating to use to select a Room. Just quit reshuffling things, like a grocery trying to hide the milk.

Please!

This answer is facetious, you describe a scenario that is not practicable as the solution, then proceed to explain how to do what I explicitly described I do not want to achieve. This is the attitude that led to the new app disaster.

Grouping all rooms together is not workable, since I might not want to play music in some rooms some times, e.g. in the night where I want to just watch TV and keep it quite in all others.

Is there a way to get the app to directly play music to a room, ideally the one already playing, without having to go through a multi-step selection process?

Hmmm

Admittedly, I didn’t understand your question. However, I have no difficulty doing what you just described without all the steps you mention. So rather than continue down a path of disagreement I’ll respectfully bow out.