I would say it is normal, because some of the models in Continuum are of "extremely high quality" Some of the meshes, and textures rival Homeworld Remastered in poly counts, and texture resolutions. Which is astounding considering that these meshes were made years before (in some cases up to 10 years before HW-RE).

I dont know if classic HW2 has a setting to reduce 4k resolution textures down to 2k, but play with your graphics settings until you find something that works best for you.