Why can't I find a job to main?

[einschwartz]

The thing about leveling new jobs at this point in the game's lifespan is that jobs really don't unfold until usually very late in the game as skills get pruned and spaced out to make space for shiny new attacks every expansion, leaving inbetween leveling very stale for some jobs (for example the highly praised reaper absolutely sucks below 80 and really only feels complete at 90).

This.
I would suggest keep playing the ones that interest you the most. Or switch between 2 or 3 of them.
Based on your post, I feel like you already gravitate towards SAM and RPR, so maining those two jobs while progressing with MSQ seems like the best option.