No you route between a few *different* frequencies with basically no delay. You only need a few frequencies to avoid interference, just colour the space so no two bubbles of transmission volume are the same frequency. (Having a few different frequencies is how cell phones work for much the same reasons.)
You've also obviously not understood the point about contention ratios; hosts are only sending for a fraction of the time, they don't need full capacity all the time. In fact most of the time they don't need any.
So if I've got an 11 Mbit/s access point, I can give ~11Mbit/s access to (say) 5-50 users and they won't notice too much difference. Essentially ALL internet access is (in reality) a contended service. You can get uncontended, it's just much more expensive.