Review Detail of troutrun in A Demon's Journey

MC is a high level demon (who also happens to be a transmigrator from earth) that died and took over the body of a young noble man millions of years later. Upon taking over the body, MC reaches level 4 (of whatever the power scheme is), kills a level 4 beast like nothing. MC seems OP at this point, but as of this writing Ch ~85, he is still at the same power level and now struggles against those very same level 4 beast that was killed like nothing at the beginning. Author is definitely trying to rein in MC's power to the extent it makes the story feel dragged out. Also, as of late, most chapters (<80) are focused on building a village and his retainers/slaves and their practice journey instead of advancing the story.