> consumers have accepted an Apple/Google duopoly over mobile computing

Consumers don't have any choice. Apps are typically only available for iOS/Android. The difference with Xbox/PlayStation is that those aren't general purpose platform. Nobody needs an Xbox to access their bank or government functions. But people do (realistically) need to use smartphones. Regulation is absolutely appropriate here.

My question to you would be: why not regulate? What concrete harm do you think it would cause?