Its bad mainly because of the divide that it has created within the community.
While in a way you are correct, its only a divide that the PvPers seem to have a problem with. the PvEers are quite happy with the situation, and as far as i can tell, those who are neither strongly PvP or PvE don't seem to care much either. I think the worst i've heard from those in the middle is that large player groups means those people are not flying in open and solo so reduces their chances of meeting people, so the galaxy feels less alive than it should be.
Not sure the latter is a valid argument, unless you believe that the active players in Mobius (less than the 20+ k members that it claims for sure) are a significant portion of the total playerbase. If they represent a single digit % of the total active playerbase, then whatever effect they are having on the BGS compared to Open players is minimal. They are also then not responsible for Open being empty. If it is the case that there is a significant % of players in Mobius, then it actually says that there is a large % of the population who want PvE, which also sends a different message, one that a lot of players do not want PvP interactions and feel strongly enough about it to seal themselves away from the possibility of PvP.
On to the solo guys, and well, they play solo for a reason. Either due to internet, or they want a single player experience. For the former, they have to remain divided. For the latter, they simply are not going to be happy in Open anyway. So "fixing" the divide is going to turn a lot of players away.
Ok, i've drifited a bit, but the main problem here I think is that only a relatively small % of the total playerbase actually have a serious issue with the divided playerbase. I'd guess a vast majority are rather "meh" about the whole thing (especially those who do not participate in forum life), or at least, when they bought the game, they looked at the mode separation and thought "ok, i can live with that".
And not having a dig at you directly here Stalker, you're a good chap and we have had good chats on IRC, but buying a game, reading about how it will work (designed to work), and then afterwards complaining about how it works, well, I think its rather silly.
Perhaps the only people who get a pass on this are backers who backed before FD announced how the architecture would work and how the BGS would be shared between modes. I have no idea of the numbers or dates of deciding things were going to be like this, but that information was advertised since at least Beta. Maybe even Alpha? How many players should get a free pass on that they bought the game before it was announced how modes and the BGS would work?