That point has some merit but it's clearly overrated to me when I compare TBC (I did a lot of 5mans back then and some raiding) to current WoW.
Right now you get the exact same experience when you try to do mythic 5mans because without a good group you picked manually you're ruined.
In TBC/WotLK when a 5man was easy to complete: it was obscenely easy to find a group anyway: I never felt like I had to do much for those.