For me it's simple: we all bought a game with pan-modal features that all players affect regardless of the game mode they play in (specifically excepting CQC). That design means that PvP is an optional extra that no player needs to engage in to participate in any in-game feature (noting that CQC is out-of-game). I'm not in favour of PvP-gating any existing game feature, or part thereof, to Open as to do so would be to force those who participate to make themselves available for PvP. If the request was for content that didn't affect those who would not participate in it then I'd have no issue.
Regarding the Mac client, that was down to Apple not updating their O/S to include the later OpenGL version required - that's hardly Frontier's fault, and I expect that Frontier knew how few players played on Mac. With respect to PvP, Frontier have indicated that, while the majority of players play in Open (at least some of the time) and Solo and Private Groups enjoy "significant portions" of the player-base, they are "well aware" that the majority of players don't get involved in PvP.
The game is still advertised as "In an age of galactic superpowers and interstellar war, each player’s unique journey influences the connected gaming experience." That's from elitedangerous.com today - so it's not that it's limited to those who bought the game seven years ago (it was pitched over eight years ago and attracted backers then, and released a bit over six years ago).