No portals is not hard really, it's just time consuming.

It is way great for immersion. There is no sailing somewhere with the bare minimum, set a portal and go sleep in your bed. You do have to make camps, find food, etc. Weapon durability becomes very important too since they are not trivial to repair.

I did a few no portals playthroughs but mistland kind of killed it for me. This biome is so tedious and unenjoyable I have no desire to really "survive" in it in a no portal run.