From what I've understood, the current meta is what a vast majority of people play into. They pick meta picks such as ahri mid or shyvana jungle, etc. People build meta builds, and sometimes they don't. However, one game has no point but to amuse. Play 100 games with that akali build, and you'll win a lot less than you would if you built her into the meta. There is a reason builds are very subject to change as items are added and as items are changed to give you the best chance of succeeding. For example, AP Vayne isn't a thing. At all. You will never carry as full AP Vayne, unless the enemy is full of trolls and feeders.
Yea, Riot doesn't want to enforce the meta, and no game company really wants that either. You don't see Pokemon having an enforced meta in competitive, but if you want to succeed at a much higher rate, follow the meta. Team Builder was an example of somehow enforcing the meta, but it is a fair enforcement. Why? It is a well-established meta that has been tested and retested by the community. This system is much better than Team Builder, in my honest opinion, as it gives you a Team Builder-like take on draft, with assigned roles and the like.
Team Builder is one of the better modes, since you could see who the teammates want to play and where, and you can accept or decline in that fashion. However, you cannot ban champs.
Since Season 1 there was the current meta of 1-1-1-2. It wasn't prevalent, since the game was brand new. After worlds, the meta exploded, outclassing the other comps. This shows that the meta was, and is, the most efficient way to win.
Now, if Riot imposes the meta, does that change much at all?
No, it doesn't. You could go into draft, and do the same shenanigans as you would in any other mode. You'd be called a troll if you just forced it, "I'm here gtfo," or "double jungle too bad," or some shit like that. If it was ok with your team, though, you would be a-ok.
Riot has a right to suggest us to go to the meta, as it has proven successful over and over again. They are in no way forcing us, or any more than they did in team builder.
If the new dynamic queue is actually enforcing the meta, it is no more enforcing than the recommended item page.
Also, league has always been a 5v5 game, and you don't need a pre-made to play!