Yes, unfortunately you are mixing up two topics.
Sure, the more carriers there are the more competition there is, but as with other things that require significant physical infrastructure (electricity, water, rail roads, phone landlines) there comes a point where having more competitors starts to get absurd, especially if they don't at least share some of their infrastructure (eg cell towers in the case of mobile carriers).
However, completely independently of how many carriers you have, exclusive carrier handset deals reduce competition. They should be outlawed. If people weren't tied to specific carriers because of exclusive handset deals they'd be able to switch carriers and thus there'd be more incentive for the carriers to keep their customers by other means such as improving services or reducing prices.
France (with only 3 national carriers and all French owned) is nowhere near that point yet. US had 6 national carriers before the pro-business Republican administration started okaying mergers left and right. Hong Kong still has 6 carriers in a small city. 6 carriers are not an absurd number of competitors.
You just have to watch right now --- Vodafone and Hutchison 3 just announceing that they are merging in Australia, thereby reducing 4 national carriers down to 3 national carriers. It's not going to be pretty for Australian consumers.
I like how you rationalize the conclusion where exclusive handset deals should be outlawed. Just look at the worldwide iphone distribution --- basically every country in the whole world allows exclusive handset deals --- only France (with their idiotic treating the symptom instead of facing the actual disease) and UAE (protecting their people from monopolistic Apple, yet screwing the rest of the world with their oil oligopoly OPEC) are voicing their "concern".
Just look at the rest of the world --- they don't even have ETF's. It doesn't matter whether there is no exclusive handset deal and there is no simlock of the phone --- the average consumer ain't going to switch to another carrier because they have to pay out the rest of the contract to their former carrier.