In an ideal world I could purchase a (usb c) dock that has some connectors and plug my awesome OnePlus 5 in to have a somewhat usable computer at home. I know Samsung wants to do something like that now (but I won't ever again buy a Samsung phone). I'd root (and pay) for a generic solution that makes my phone usable on a big(ger) screen.
Android phones have been able to connect to bluetooth or usb mouse and keyboards since nearly the very beginning. The only thing 'missing' is the screen. Samsung (and other) phones have supported external screens for many years now, often via MHL (although, as you say the Dex dock now packages it all together). I don't believe that the OnePlus5 supports external screens, but I may be wrong. You might be able to get s…
And while there were options to do that in the past, all were one-offs and needed an extra port. So I guess we both agree about the capabilities that exist(ed), but that is exactly the reason why I posted my "In an ideal world" wish. There is no solution today as far as I'm aware. Which is a shame, given the power that these smartphones have.