Tl;Dr The nether should have a bit more for certain players to make it their main/self-sufficient base.
The 1.16 update added much more to the nether dimension making it more lively, varied, and interesting, and it even began carving the way to start making bases in dimensions other than the overworld. However, I believe the nether needs a bit more to be unique for base building and have a chance at competing with the overworld.
So, I propose Mojang should add not only a bit more biomes or mobs in the nether, but add ways players can make more self-sufficient bases in the nether. These mechanics would have to center around the nether's playstyle of a harder land, make up certain resources/mechanics the nether lacks (i.e. paper for enchanting and other purposes), and give way to creative solutions to make certain activities that are easier in the overworld work better in the nether (i.e. You can farm more easily with bees on your side in the nether).