Like the discussion i was having with Fencers, this is what i was trying to get at, but ultimately as a non-native english speaker i can't get across.
If you are playing Diablo 3 during a Season , and you aren't playing in Season mode, you are effectively gimping yourself out from exclusive transmog, banner, achievements and first dibs on new build/character changing items.
To not play Season mode during a season seems and feels like the wrong thing to do.