Oh no, i'm getting it. You're missing the major point.

But the biggest problem is people who do not have the correct rank play in party and mess up solo games!

I'll quote from before to rebuttal this statement

if you rate it lower then that's your problem to deal with not Valves.

If the queues were separated, almost all of these issues would be fixed!

No it wouldn't. In every single scenario you have mentioned including your own. If they separated the queues you would be put into a 1.2k with your friend? Yes? Then the "problem" isn't fixed. You're just forcing other team ranked players to deal with it. You're still a 4k player playing in a 1k bracket if the queues were separated.

Thus the problem you're mentioning isn't fixed.

You just feel as if it is because you only play solo (rate solo higher) and think "if it doesn't effect me it isn't happening"

Again

if you rate it lower then that's your problem to deal with not Valves.

Your entire argument supports re-calibration after not playing either team or solo ranked after X amount of time. Nothing you have said supports separating the queues. It doesn't fix a single thing you mentioned.