Vael
Legend
What we need is an additional layer of design space for character building. Where is the 5e version of Themes from 4e Dark Sun?
Power creep be damned; more modular opportunities for characters above and beyond the slow trickle (if used at all) of feats would provide a space for a more unique character concepts and class-agnostic setting tropes (Dragonmarks, Guilds, Magic Schools, Knightly Orders, etc.)
I agree, character themes as an additional thing for PCs would be a good idea. Using the existing options for Char Gen are clearly getting slightly strained, not everything fits under the aegis of Lineage, Subclass or Feat.
And themes need not be for PCs. How about Monster themes. Augment all these goblins with an "Acolyte of the Demon" theme to make them scarier in combat.
Ultimately, I agree, trying to stuff new things into existing framework isn't always the best answer, give us new design space.