Playing with others is fun. It's nice to have others around to help with the grunt work, gathering resources, building your base, fighting beside you 'n' whatnot.

Enemies do scale with the number of players nearby, but having another person around can help as they get in hits while you block/flee. It also only matters if others are nearby, so you can still adventure by yourself and not worry about scaling while other players are doing their own things.

The swamp is a filter. It filters out the real vikings from from the milk drinkers. You've got to manage your stamina better, go in as prepared as possible, and properly prioritize threats. As with all new biomes, it's toughest when you first arrive, and all of it gets much easier as your gear and meals improve.

And if you're really struggling, there's always mods. You paid money for the game; you should be able to enjoy it. Tweaking things in various ways so that you can enjoy the game is a potential route you can take.