This feature is very important. It would definitely solve the serious problem that occurs when you selectively disable plugins on specific pages that would depend on other plugins.

WordPress gives you the possibility to filter the core option "active_plugins". This means that if in a plugin you check the presence of a third plugin by looking at that option, and in a mu-plugin that option is filtered, you may think that plugin is active, but it isn't.

Some plugins use functions defined in other plugins without checking first the existence of that functions, but only checking the core option "active_plugins". I have seen a lot of these kinds of plugins. When you have this kind of plugin and you selectively disable plugins on specific pages, the risk you have a fatal error is very high. Plugin dependencies managed by the core would avoid this kind of issue.
I really hope this feature is implemented in the core. I also ask: why not? What's the downside? The supported versions are another topic.
If plugin B needs plugin A, it will always need it. I agree that this is a necessary but not sufficient condition, but let's first be sure the necessary condition is satisfied, and then the version compatibilities can be managed by the code of the plugins. The necessary condition that plugin A must be active should be managed by the core.

I don't understand why after so many years this feature is still not implemented.