So if Riot isn't bringing back solo queue, can we talk about why ranked teams aren't a thing?

So I was always a big fan of premade teams. It was honestly the best time for me to be in a group that was actually looking to work on rotations, dragon pressure, teamplay, etc. This was the season that I had two separate teams with time to put some practice in, but then dynamic queue came around and I never got the chance. While I can now play in a group of 5 in dynamic, a both of my teams have players spanning from bronze to plat, making us unable to queue as 5. This would also mean that if the higher ranked players wished to climb to diamond, then all of our players would need to rush gold. I understand that if we all queued together we can climb together, but part of the problem is that our higher ranked players climb due to having a lot more time to play ranked. I don't want to limit their climb just so we can rank as 5, but I miss the chance that ranked teams gave us to play and be ranked by how we played in OUR team, rather than the how well we play in a team in general. I'm extra curious about this because of the fact that Riot said that they're looking into removing anything above a trio queue for higher MMRs, where exactly will 5-stacks be playing beyond that point?

Bonus question: Sorry to tack on extra bits, but I've been wondering how the challenger series works now that they don't have ranked challenger teams to pull from. Has Riot released a comment or an explanation that someone could link me to about that?