The whole point of the network effect, is that there can be more than zero competitors who even have a superior product, and it really doesn't matter.
In fact, you can have "competition" while having all the substance of the monopoly. For example, if there are eight competitors with equal marketshare, but it's impossible for anyone new to enter the market, those eight can easily conspire to charge monopoly profits, despite each one's "small" market share.
That's a distortion. It's more like, lots of people are dissatisfied, but all of the alternatives are economic/network-effect suicide. It's more like people living and working in the crappy mining town, because the only alternatives are like living as a hobo in the woods.
Toy example: if everyone demands at least $30/pound for some risky kind of coal mining, because it's such a pain to do and they'd rather a) rest or b) do easier work at any lower price ... that doesn't mean coal miners are colluding or that coal mining is a monopoly.
In that case, if you want a $29/pound alternative, your desire is economically unrealistic.
If there's a single coal miner that does it for $29/pound -- and is thus the most efficient one -- that miner will dominate the (tiny, niche) market. But it would not rightly be called a "monopoly", but "a single provider who is legitimately better and would lose business if he started to falter".
Telling me that someone currently dominates a market does not prove monopoly power.
I can picture a scenario where some sites have an insurmountable advantage because of compromised network neutrality. I'm very sure that in that case, the winners would be crowing about how, "the market has spoken," when the reality is that the market is broken.