I check the Time Machine menu bar indicator too, but the question is worth asking: Why is it so important to know if Time Machine is active? Apple designed Time Machine so that we don't have to think about it. If Time Machine is in the middle of a backup and I close the lid and take it out of the house (away from my Time Capsule wifi network), nothing tragic happens. Time Machine gracefully and silently recovers, switches over to local mobile backups (which have no indicator at all), and when I return home and plug in the Mac it picks up again where it left off.
The way Apple changed the icon seems to be in line with Apple's general philosophical trend of wanting to help users focus on what they are accomplishing with the computer, not on the computer itself. Kind of like how in iOS where the exact battery percentage readout in the top status bar is not turned on by default. Apple seems to want to get away from encouraging people to micromanage their systems, especially when it is not necessary.
And I'm talking as someone who sometimes opens the Time Machine preference panel to see the entire backup progress bar and stats and will often wait for it to complete before sleeping the Mac. Even though that behavior is not necessary in the slightest. Yes, micromanaging a modern Mac is a little silly and I am a prime example of that sometimes.