I think the problem with ranks in Halo 5 is a lot of us want one thing while really they have been created for a specific purpose. Personally I want it to show how good/bad I am, be something to work on and be proud of achieving to show off basically. Like the good ole' days.
Whereas the system has been designed more as a... "Right people want a shiny symbol next to their name, lets create a system that attributes their behind the scenes skill level with a shiny symbol so they don't moan". It's less of an achievement and more just a here is my current category. Which is why the placement matches can put you in Champion if you're the first to hit Onyx. It's not meant to be a big flashy achievement, it literally is just matter of fact, here I am.
The same reason why Champion is a thing in general. It's just to attribute the current highest people with their own distinguished rank so it is easily identifiable. It's not meant to be some super crazy rare thing you work months towards, it's just a matter of fact. This guy is 33rd in the world right now, sorted, get over it.
Or maybe I'm rambling and need more sleep ;D