The entirety of the game is fine to play solo. The bosses and even the later bosses arent much of a problem with a minimum of planning, like making a small arena for the fight or using the right type of arrows, staying on top of keeping your gear upgraded and actualy making an effort with the food preparations.

At most ppl got a valid complaint that the experience is going to feel a bit slower, but the difference between killing a boss in 2 minutes or 4 make little difference.