So you think that cars built by 1 company providing engines and then another company sells you the cabin to put on top?

Should rocket companies not be able to build and launch rockets, or their own sats? Should we prevent Tesla from making batteries? Should Apple or Oxide (if you want a startup) be prevented from developing software and hardware together? What is that other then vertical integration.

Vertical integration is everything, being against vertical integration means that basically every company should only ever be allowed to control a single step in a production process. And its hard even define 'a step' even means, as even things like making steel requires many steps.

If you want things, at least actually figure out what you want because I don't think that is it.