Is multiplayer easy?

Hi! How are y'all

I've been playing Calamity + Thorium + Ragnarok with 3 other friends but I feel like the boss fights haven't been hard really. I also don't like, and don't know how to turn it off, the spawning a boss won't consume the item. So you can spawn it endlessly and get tons of loot (am I wrong about this?)

I've been playing in Normal difficulty. Am I supposed to keep playing and find it hard later?
Should I change bosses settings?

I need any advice you can give me :D