The parking lot analogy feels really reaching, tbh. This is a magic world where everyone has powers and it's incredibly violent just by it's nature. If this were transferred into our modern world, people would be getting killed over stolen parking spots too. That's a goofy thing to say. This game isn't trying to recreate some simple, peaceful, streamlined experience. It's supposed to be chaotic, and dangerous. It's the World of Warcraft. The idea that people can come up and kill you is one of the only exciting things that can even happen when you're running around the open world. The monsters are barely dangerous at all once you have any kind of decent gear. You're just arguing for a more sanitized, boring version of the game where you can just log on and do your chores without anyone bothering you. Go play Stardew Valley if that's what your into. Don't ruin it for the rest of us by crying about getting killed in an online game.
"Stop whining, vote for PVP by enabling PVP in the game and leave us PVE people alone." - This is such a dumb comment.
This skews the way world PvP operates enormously. It's now a totally different game. You've distorted all world PVP interactions. The person who is flagging themselves has so much more risk than they would if everyone is PVP. In a realm where everyone is PVP, you can proactively kill people you see eyeballing you or getting a little too close for comfort. In this scenario where you have to flag yourself, non-flagged people can just walk up to you and posture. They can troll you by tagging your mobs without you having the ability to fight back, or just staying around so you can't get to low while they have absolutely no risk. It basically turns everyone into a rogue. You, as the non-flagged person get to pick the rules of engagement which gives you an enormous advantage. All this leads to is nobody PvPing while leveling because the risk far outweighs any "reward" of having some fun. To act like it's totally the same "just flag up" is dishonest or ill-considered.
It's not spoiled toy say that this extremely impactful update to the game makes me not want to play. It's a very big change to the game. As i said in a previous comment, the different between WPVP in PVP servers in Normal/PVE servers is pretty enormous. The dynamics around world PVP are inherently changed when it's optional. If you don't understand that, i don't know how to help you. My point about comparing the games, is that i feel as though people are trying to turn WoW into a very sterile, almost single player, type of game. It appears that you don't want to deal with any chaos or randomness in the world. The game is pretty stale without the world PVP aspect and the random violence that can occur between two people who just pass each other on the road. Everybody out in the world has the same danger and sense of alertness. Of course i could just flag myself and wonder around, but then i'm putting myself at a big disadvantage.
I think a better idea would be to keep it as a pvp server and then implement an honor system that punishes people for camping or killing people of a much lower level. This is all very possible and not a novel idea. I believe that most problems can be solved by balancing and aligning people's incentive. Another option, as others have said, would be to make it Pve, but then give some sort of incentive for people to flag themselves (increased XP, Rep, Gold). As it's looking right now, it's not in my best interest to flag as i'm immediately handing over the opportunity to set the rules of engagement and stack all of the odds in your favor.