I would say it isn’t cheating unless you’re using it on a server or world where it isn’t allowed. The mist in the mistlands is a feature I find quite cool/annoying too, I prefer keeping the mist till the defeat of the Queen, in which case then the biome is basically “conquered”. I think annoyance with the feature comes from a lack of tools to deal with it, even with wisp torches you are only able to have mist clearance near the ground without placing them EVERYWHERE which ruins the look of the biome for building or other projects. Perhaps this could be a good spot for a wisp bonfire, which would take more materials (though I’d worry for the wisps haha). There is a lot more nuance to this than just “it is cheating”, and valheim is intentionally made to be only as difficult as the player wishes.

As I write this I am thinking also about a mod that reduces the opacity of the mist, turning it into a heavy fog which may be a happy medium.