Atmos has height channels added to the audio track. So you'll either need speakers in your ceiling or a setup which tries to emulate that by bouncing the sound off the ceiling to really benefit from it.
The confusing thing about Atmos is that there are basically two versions of it. There is the TrueHD version that you get on BluRay discs which is the highest, uncompressed quality. And then there is the streaming version which uses Dolby Digital Plus as a wrapper for a compressed version of the audio signal.
Atmos on its own really just tells you that there are height channels. Dolby has made all this stuff quite misleading and confusing to the average user.
I've seen multiple things be deprecated while at Google and I can say that the things I saw killed from the inside (because it was a product I worked on) in the past 5 years were either not being used by many users anymore or had an alternative that had similar features instead.
So if you depended on it, you could depend on something else. And if it was successful, it wasn't canceled.
I didn't work on Stadia but I imagine that it was a huge waste of money for the company for the relatively few users it had. If they could have offered a good subscription based service like Xbox Game Pass or Apple Arcade I'm sure it would have more users. But getting access to content would be very expensive. At least they refunded consumers' money for the games they purchased.
You're implying that engineers have a say in product decisions. They often don't. A lot of what we are told to build comes from upper management unfortunately.
I wouldn't blame eng interviewing practices on this particular issue.
There are other reasons too like scale. Obviously not everyone can work on those types of projects but few companies can claim their engineers' code will affect a billion users for example. At that scale, the problems that need to be solved can be interesting even if they're trivial for a smaller set of users.
https://twitter.com/searchliaison/status/1790473952256786805