lets start with the swamp, of all the current biomes in the game, the swamp is the only one where i can see NO benefit to living there
meados: chill enviorment with flat areas
dark forest: good supply of resources like wood and stone + good money from troll hunting
mountains: highly defendable + doggos
plains: access to endgame materials and food like lox and grain

swamp has nothing like that. want to build on the ground, hope ya like having your base flattened by a wandering abomination. want to build up in the trees? oh you thought minecrafts phantoms were bad? wait till you meet the wraith. only good materials here are iron and *arguably* crafting items like entrails and guck

oh right... iron

bronze was a pain due to requiring 2 materials that weigh a ton and can't be teleported, but usually they're found on your first spawn island, swamp? no such luck. if you're unlucky your island won't even have a swamp, or atleast not a usable one. meaning you'll have to ferry iron to your base because for SOME REASON metal ore and bars arn't able to be moved via teleportation (yet somehow me wearing a full suit of the stuff + weapon, shield and enough nails to make a backup ship is perfectly fine) on the bronze ship no less, which only has a capacity for 4 stacks. spoiler you need A LOT MORE than 4 stacks. you need to craft the following:
a full suit of armour
a weapon, sometimes 2
a shield
a new set of tools
new crafting station addons
stonecutter
new boat
and thats NOT including all the building parts that want more of that iron OR if you want to refine any of that gear
and to get all this iron, you need to:
have good quality bronze level gear
a good blunt weapon
a good ranged weapon
high level food
the ability to fight multiple mobs in a constantly wet enviroment with both melee and ranged fighters
and enough anti poison mead to drown an entire village

and if per chance you wanted to make it easier on yourself, all you have to do is go into the higher level area, braving dragons, wolves, and freezing cold, looking for a metal that you can only really find consistantly with an item you get by beating bonemass, speaking of which

bonemass is probably the only boss i would call unfair in this game, all the others had easy cues to recognise
boss 1: large target in a crouded wood, loop around obstickles and whittle him down when he presents an opening
boss 2: large slow moving enemy that deals high close range damage and summons melee focused minions. stay at range and take down with fire arrows, done and done
bonemass: high melee damage + poison clouds. ok so this must be another stay at range and whittle him down one right? massive resistance to arrows... unless you go to the mountains to get freezeglands.

how i'd fix:
reduce general costs for iron gear
lower the stats on bonemass and the enemies in the swamps
add some kind of buildable thing to keep swamp enemies at bay, like with greydwarves and campfires