There are so many holes in your logic it's almost not worth this reply, but I am always trying to help the lesser, so here it is:
Your comparison between real sports and e-sports is extremely flawed. In E-sports, theres ranked play and then professional play. In real sports, theres just professional play. You hardly ever see hobby leagues, and if you do, theyre almost never an actual organization and more a group of guys or gals who play against each other.
Just for an example and I can pull about a thousand others... http://www.dmhl.ca/ - http://www.leaguelineup.com/welcome.asp?url=tbaleague
You clearly are not one of organized sports. That's okay. There are TONS of "casual leagues" (normals) for playing real sports. The world of E-Sports and "real sports" is not all that different.
Moving on...
Unlike real sports, E-sports tend to have a gradual progression from unranked to professional. You always start as un ranked playing for fun, but as you get more serious you move on to ranked and try to better your play.
Almost right, except that the progression is from UNRANKED (normals) to RANKED (Bronze, Silver, Gold, Play, etc etc.) This is the GAP. Repeat. This is the GAP.
Moving on again...
What youre suggesting goes against the very core of the E-sports ranking system. It excludes an extreme amount of people for no other reason than "because you should be good already!" With your suggestion, we wouldnt even need the tier system at all. With your suggestion, ranked would essentially become premade 5v5s competing in a roster style ranking with the top 10 teams being "professional".
Just wrong. What I am suggesting is VERY simple. It weeds out the serious player from the casual player in an environment that is meant for the serious player. Again, comparing to real sports, you don't see any "beer league" players that play in competitive play, where you would be scouted for professional play.
Now, when an athlete wants to join the competitive scene (ranked) they have to try out. This system has been in place and has worked for years. This even goes for sports that are individually played. If you want to argue the semantics of sport, this is not the place for it. The problem here is that there is no way to try out.. you automatically gain access by putting time in. Flawed? Yes.
So, instead of 'trying out', because we know there's no actual person or system in place to weed out the baddies, I propose these ranked requirements.
Perhaps the entire system is flawed, but there sure as hell are too many players cluttering the Ranked ladders. Maybe it would simply be better to have "Normals" and "Pre-made Ranked 5s". Ranked Solo Q might just be the problem altogether considering its "SOLO or DUO" in a game that is 5 PLAYER TEAM oriented.
Will Riot remove Ranked Solo Q? I highly doubt it as it's one of their addiction devices (come play the ladder, see how high you can climb).
So, let's just make it better. These requirements are one step towards that.