They're not going to be able to retcon the game's history and development. Again, it's a logical fallacy. The best they're going to be able to manage is alienating part of the player base- (and it's going cost them if they do) or retract the stance and accept that PvE players have just as much right to "de facto Open" as PvP players do.
Which is why adding an Open PvE mode, considering mode parity as is a given, is indeed the best solution. The current Open would still stay for those that like the thrills of getting ganked.
As said before, Open PvE is possible with certain concessions to the game physics.
Perhaps, if such a separation was added, the impact of blocking even can be reduced.
Because blocking inhibits those that have a CGNAT or DSLite connection from instancing as being blocked by the only directly reachable peer can negatively affect your ability to instance if you are not directly reachable (which is also why you sometims get Orange Sidewinders and Mauve Adders because you cannot recover peer connections relative to your instance because the other peers are not directly reachable as well).
Frontier intentionally skimps on TURN relays because AWS instances are costly.
Perhaps they should consider
optional integration of SDR (Steam) and/or EOS (EGS) as additional means to instance because both services provide TURN relays for free, using their respective CDN for data transport.