First: "that is not an argument" is not a counterargument. You are again just ignoring my arguments, which is not good for out conversation
2nd: We both know different people then
But let me set up a scenario for you then to help understand my point of view:
You play in a semi-hardcore guild in TBC and are so good, that your team is able to kill the first boss in Sunwell on the 2nd week. You are now among a small procentage of players, who are good enough to kill anything in there. You do good in there in the following weeks and clear more content. You have a casual friend, who after hearing your stories about killing Brutallus and seeing Felmyst rise, want to join your raid. He is though not good enough, so you say to him "Get better and we will invite you". That friend then gets better and better, gets more gear and becomes a good player. Try imagining his thoughts when he finally gets invited to Sunwell and you start clearing mobs. This guy has proberly tried to do the instance before with another group and proberly wiped several times on the firsts mob, yet you are now clearing everything like a group of professionals. That experience is proberly gonna knock his socks off, because he is experiencing completly new content all because he became good enough to keep up with your group. Again, ask anybody who has taken this leap and they will tell you how amazing an experience that is.
This scenario is not really happening in the current form of WoW. Unless you are keeping yourself totally up to date with all raiding content, there is a high chance, that the first time you experience a boss, is actually through LFR. This means, that the following experience is not gonna be that amazing, since you are just seeing the same guy, but in new clothes. Better gear is a reward, which is dwarfed when put besides exclusive content.
And again, i am not talking about barring people off from fun, ofcourse people should always have something to do, but i really do believe, that people should have content as a reward for engagement into the game and becoming better at the core gameplay.