I upgraded from the abyssal razor to a silver knife yesterday, making it level 4 right off the bat. I can now one-shot wolves after parrying them if RNG rolls a high damage number, which is extremely useful in the mountains.

I don't know about Plains yet, but other than that and those enemies that really require a blunt weapon, a knife with a light shield absolutely is viable throughout the game. The speed of attacks is invaluable and you can even stagger-lock enemies.

I don't see why I wouldn't be able to handle Plains enemies with a knife or bow. I already know a bow is very good there and that the mosquitoes are easy enough to parry.