I don't think it prevents champions from being played in competitive, I think it enables champions to be played in competitive.
To the best of my knowledge, lane swaps are done when one team's bot lane would have a terrible time at early levels against the other team's bot lane. Rather than write off certain champions all together, they swap with the top to get the early levels and farm they need to be able to be viable later in the game. To the best of my knowledge, this hasn't crowded out any top lane picks, since if it's unfavorable for the top laner to go into a 2v1, then they hang out with the jungler to get the experience and gold for the first few levels.
Really, I don't see this as a competitive problem. You can argue it's a spectator problem, but not really a gameplay problem.