I have 21 level 100's, all of them are at LEAST 675. Thanks to timewalking and baleful tokens and Kazzak. This was done to prepare them for the gold haul that is Garrisons. Currently at 3 million and still going.
However, before this I had 12 toons.. one of every class and one on Horde. I did indeed "actually play the game" with all of them and enjoyed the different mechanics. I didn't raid on all of them.. didn't even LFR on all of them.
Your speculation as to people with and without "lots of alts" is just wrong. I've been playing this game since the beginning of BC.. so 10 years. And in that time I have switched mains a couple times, and leveled alts the old fashioned way.
Alts are a way for me to experience the same content differently... as opposed to grinding the same dungeons 400 times... I can do them a few dozen times on 12 characters... who is actually "playing the game"?