But those two ideas aren't mutually-exclusive. He's still right when he says the point of an MMO is the appeal of playing with other people. It's defined by the word "Multiplayer". And you're right in that there are solo activities and you're fully allowed to do your own thing and go by the game by your lonesome. However, this is still at the end of the day, an MMO. The focus of the game won't be the single player activities, but rather the multiplayer ones.
Obviously, we shouldn't discredit people who want to do their own thing, but catering to them too hard is going against that "Multiplayer" aspect. The person next to you brings up a really good point that I'd like to illustrate with my own experience.
I do have social anxiety. Oh I'm fine and extraverted online, but when I don't know the environment I'm going to shove myself in, I basically freeze into stone. Going through Sastasha to Copperbell was an exercise in obssession. I didn't "study" Mizzteq's guides for something that now I take for granted. I went absolutely insane trying to figure out how the dungeon was like because I didn't want to make a complete and utter fool of myself. By that I meant stuff like "any maps? What animations should I look for? What's she doing as a tank so I know which button to press when?". Ifrit was so bad because "oh it's a standalone boss, he probably is very hard" to the point where I cancelled my queue about five times because I was having panic attacks.
A lot of it came from how I imagined the internet would be. Sure, after that it got a lot better because I realized it wasn't that bad. Then I got into an FC and slowly that anxiety went away. I still feel it when I join for Savage content, which is why I at least try to watch guides to have a notion of what I'm going to do. I will fail, I will wipe, I will likely even cause a wipe. But I know now that I can learn and most people will be patient.
But I knew what I had gotten myself into. I knew this was a multiplayer game and that I needed to be in a party with other people. That was its focus, its appeal, and thus I had to respect it, and I didn't question whether maybe they should have changed it. It said so on the label: "MMORPG". My anxiety comes from my own self, from within. It's not videogame anxiety, this crap plagues me irl to the point where it's a medical concern of mine. And while it's not healthy, at times I forced myself to go through content, disable chat and pretend the others are NPCs. Because to me, I paid for the online multiplayer experience, and I wouldn't be here knowing that if I didn't want to.
Of course, this is just my experience, and some likely have it far worse, others have it far better. Just because I pushed myself doesn't mean others have to nor that it was okay to begin with. But there is a bit of awareness to be had with the "Multiplayer" aspect of the label, and unfortunately, we can't deny that it brings along an expectation and standard. It shapes what we're going to interact with. We might have ways to mitigate this and help people with anxiety to feel at ease, but in an MMO, at some point, other people will be around.