If you have a turntable signal going through a D/A converter, you may as well just play a digital source.
Inserting an ADC / DAC step into an audio chain does not cause the sound to completely lose the character of the incoming analog signal. I don't think one would argue for using a MIDI keyboard instead of a real piano even if the recording is going to be digitized.
If the overall result is a net positive, then this is a worthwhile addition. If someone prefers a preamp that does happen to perform an ADC on its analog inputs over one that does not, I would tell them to pick the one that does the ADC.
Other benefits may come from being able to apply DSP, or from using a digital volume implementation that is better than the other (analog) options available to someone.
I have heard Atmos from a high end audio store and I was not impressed. I cannot get use to sound coming from the ceiling as opposed to the horizontal plane. I don't even like room correction as the sound is different in every seat in the room. The only time you will hear object based in real life is in your home theater with Atmos. You won't hear it in the real world.
Atmos is certainly a preference, similar to surround sound versus stereo, or stereo versus mono. But object-based audio is what we hear in the real world all the time, and is also the basis for stereo music playback. The timing and volume of sound produced from the two left and right speakers is based on where the original sound source would be, either computed or recorded using a stereo+ microphone.
Surround sound is a direct extension of that principle applied to multiple speakers, whether they are on the horizontal plane or if they also include height speakers. Object-based audio lets you encode the audio separately from number of and physical location of the speakers in use. Prior to object-based audio, the sound was mixed with a fixed speaker setup in mind. Effectively a single mapping of object-based audio onto a specific speaker setup. With object-based audio, there is now the option to dynamically create the mapping that works best for an individual person's speaker setup (although still assuming a fixed set of potential setups based on recommended configurations; using a processor that actually locates the individual speakers allows for truly custom dynamic mapping).
With respect to room correction, the sound will already be different in every seat of a room. The goal of room correction is to minimize those differences, and we know it can do this based on before and after measurements. It is certainly the case that some implementations are better than others.
