I let you take a look at french D1.
At the moment the blue conference has won 10 consecutive titles, still in progress, and we often get the best promoted teams... Fresh example last season with the two undefeated D2 teams joining us. And I know this problem also occurs in other divisions.
I don't know if the promoting system is totally random and if this is just bad luck, but yes I understand that people want to change things.
Telling that time will balance the conferences' competitiveness isn't true, or at least not always in a decent time span.