I have had the honor to play with all of the divisions you have listed and I'll chime in on my thoughts.
I'de say mid Bronze to low Gold are around the same skill level (At least in my experience) and if you're in there, you can hold your own against them.
Mid-High Gold is when people seem to start to get a pretty good understanding of mechanics and how the games are supposed to go.
Plat-Mid Diamond is when people actually start to get "good". These people know the mechanics and can put them to practice, just not 100% of the time.
High Diamond+ is when you are in tuned with the mechanical complexities of this game and you're an extremely good player. You know what you should be doing at all times to maximize your chances of winning. Objective control, farming, when and if you should engage in fights, you name it.
Just my 2¢.