Without doubt. But there's attracting players, there's keeping players, and there's keeping players enthusiastic. I imagine someone who's never played the game would be drawn by the theoretical appeal of 'play your way' - the ability to choose whether to allow interaction or not, but everyone plays in the same universe anyway. That does sound pretty great. And I've no doubt there's a substantial number of people - and obviously enough people for Frontier's needs - that're happy enough to keep playing.
But it's objectively true that there is a lot of conflict amongst players over the interface between the modes: a casual glance over the forums demonstrates that. And as far as I'm aware it's been like this at least since beta, and certainly since release. My perception - for that's all it can be, without access to solid user data - is that the inherent conflicts between the different play styles that ED is trying to accommodate make it more difficult for the game to truly excel at being one specific thing. It's a jack-of-all-modes.
I didn't see that stream. But I wouldn't disagree: the game hasn't been marketed as PVP, which is at least partly the problem. It's been built and marketed as a multiplayer game - on the back of a franchise that built popularity and a 'cult status' without ever having previously offered multiplayer - and a space combat game. So whether or not DBOBE ever actually said "This is a PVP game", that assumption is going to be there. It is a game where players can be destroyed by others. That means it will attract players whose preference is to fight other players (I make no moral judgement here - it's just a statement).
At the same time, players who heard the game not being sold as a PVP game, but were drawn in by the promise of peaceful or constructive interaction with other players are... well, they're probably in large part the population of Mobius, and those supporting an optional Open PVE mode. Because to them, even though it's not been marketed, designed or intended as one, ED is a PVP game to all intents and purposes.
As you say, we'll never know what could've been. And I can't know how many people have dropped off playing or wandered away from ED entirely, and how many more have started up. This isn't an 'ED is dying' post, it really isn't. I have no way to know how well the game's doing, and I hope it's doing well. But still, my strong feeling remains that had Frontier chosen one thing or the other right at the start, if ED had been specialised towards PVP, or Open PVE, or Solo play (or even the notorious yet mythical offline version), it could have forged a clearer path for itself and catered better to its chosen player base.
Just as a FYI : David Braben stated the "never sold as a PvP game" in this segment from a recent livestream...
[video=youtube;n7tGV7VVlhE]https://www.youtube.com/watch?v=n7tGV7VVlhE[/video]
Regards