I think possibly you're confusing MHX2 and the importer in MPFB (makehuman plugin for blender). These are unrelated.
MHX2 is the old style file export format. You use this by exporting a file in makehuman and then importing that file in blender. MHX2 is developed independently of makehuman, and development has stalled a bit lately. To get a version that works with blender 2.80, check out Aranuvir's fork at https://bitbucket.org/Aranuvir/mhx2-mak ... downloads/
MPFB is the new style connection between makehuman and blender. It does not use any file exports at all. Instead it enabled blender to communicate directly with blender. To enable this in blender you should install the plugin zip found here: https://github.com/makehumancommunity/m ... stribution, or use the same file shipped with the alpha.