To be fair I agree. I had a dedicated world with three of my friends, it can't handle it. With four people in game it causes the hosts game to crash every 20-30 minutes, that's not bad for the dedicated people, however when it does crash for the host there is a chance that some parts to people's bases can be deleted, as it happened to me and my friends a considerable amount of times. It's sad to see, the game is good, the only thing holding back the devs of the game I imagine is money and hardware limitations.
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The thing with having max four people per lobby is for a somewhat stabilisation for the dedicated server. Even with four people it still becomes unstable after some time, which leads to crashes and parts of people's bases being deleted.