Unlike League of Legends, Haven has so much PvE content that it can be enjoyed as a PvE-only game. Even LoL had PvE game modes like Swarm that were very popular.
Would players still enjoy Haven if it was reduced to a PvP-only game mode?
Make PvP fun for all participants and players will stop asking for it to be removed. It's very simple.
Maybe, but not by much. We can even make a rough estimate:
1) Classic PvE ("battles" against monsters). Haven has several dozen monsters and animals to fight. However, most battles are fairly similar, with the following exceptions: mammoth (killed with a feature/exploit), troll (killed by swimming in a boat in a circle), and probably bear (can suddenly hug + rage). Everything else is killed by leading to water (or shore) and then outreach. If they removed this, it would just be killed in the face, but later with better stats and equipment.
2) Dungeons. Copypasta. There are probably only three unique features - the "riddle" in the bee dungeon, purple bats, and the fact that water works on beavers.
3) Character development. Finding meta food and farming the same ingredients. Same with LP. At some point you don't even need to leave the safety of the base.
4) Equipment. Essentially, there are two and a half types of weapons (three and a half, if you count r bow). Obtained the same way - by farming materials at the base. There's one type of armor. Everything else is just basic gear, worn until the mine can produce steel.
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All of the above can be done solo in a single world, essentially completing the game. And all the so-called "PvE opponents" have long since done so. You might think Snail, for example, never planted anything or fed the pigs, but you're simply wrong. The thing is, it's not all this that keeps the "smurfs" in the game.
PvP adds that secret sauce to the game - you can quickly lose everything, or suddenly accelerate your progress incredibly. Fear and greed are genuine feelings that drive us to act, to worry, to form groups. Without them, there's only apathy. And apathy is death.