I think people often get hung up on certain features defining an MMO, for example "guilds" as being some sort of prerequisite. Maybe sqaudrons will check that box for some people. Doesn't make it more of an MMO though, being an MMO is not contingent on the existence of guild like mechanics. This doesn't mean ED is not an MMO.
Some people get hung up on how many players you can meet at a single time, which is also a bit of flawed thinking. Look at some MMOs when it comes to how many people you can meet and how they work. Games like WoW for example have low network overheard. In towns, yeah, you can see lots of people, dozens sometimes. (most of them sitting around spouting rubbish). On raids how many do you usually see? You and your mates, perhaps encoutner another party. On big raids how many, tens? But the network overheads for a game like WoW are pretty low, and you can use some funky tricks to smooth out the networking overhead. There is a rather good article on Age of Empires about some of the tricks they used to get that working well over the internet with the high latency of the times using tricks to provide a good experience. I'm sure some of those same tricks are being used in games like WoW. Then you get games like EvE, where they handle high load by slowing the whole game down. Not something that can be done in ED. There are instance limits due to the nature of the beast, and even C/S based games can struggle once you start piling on the players. This is why many arena FPS limit the number of players to ensure good performance, and even then, you get people lagging out and often you play on regional servers. In ED i can meet players from all around the world, unlike some games, where to meet players from other parts of the world unles i join their regional servers, and suffer higher pings for my troubles and am at a disadvantage. Even the newer generation of arena games like PUBG are not immune, and notice, you don't really interact with more than a few people at any time. I've played some Fortnite recently, and once you are out of the plane, you usually meet only a few people at once. And you can still lag out. In ED we have seen up to 100 people in an instance (which was flakey), but it means that ED is up there in terms of people in a single instance, even if it isn't the norm. So, number of people in an instance can't really disqualify it either.
Some people get hung up on modes, saying a proper MMO shouldn't have modes. Don't see how that disqualifies it either. We share a common galaxy and can choose to play together or separate. Some MMOs allow private servers (Neverwinter Nights 1 and 2), some MMOs have offical PvP and PvE servers. People say ED's modes fragment the playerbase, that's nothing compared to the fragmentation that occurs when you allow private servers or separate official servers. Hell, the bigger MMOs have dozens of official servers where you can only meet people on your server!
Some people get hung up on P2P rather than C/S. Again, the phrase MMO is not contingent on the network architecture used. There are even some bonuses to FD's hybrid system that is used. For example, the ping between any two participants is identical. If one person is lagging in the eyes of one, then the reverse also applies. Unlike with C/S, a non lagging person has an advantage over someone who is lagging. In ED, everyone is equal in relation to each other. The matchmaking server does its best to try and not put people with bad pings in the same instance, but doesn't always get it right. Anyway, it still doesn't disqualify it as an MMO.
Overall though, at the end of the day, its just a label. ED is a game, which you either enjoy or do not. The label used is just a label. I enjoy single player games.... which are not MMOs. Does that mean they are not good games because they are not MMOs? Of course not. All that matters is the game.