isn't that done on purpose? The fMC and MC are both scumbags of the worst kind with no care for others. The whole point is for them to be always trying to one up and trample over the other while pursuing their selfish goals. I'm not paying much attention (if any at all) to the story, to the demons, to the royalty and whatever their business is. This is all part of the stage for them to do the comedy skits while the background noise misunderstand their cheap acting as genuine acts of care, compassion and heroism.
As long as there is good fun to be had I don't care if the story goes on for 20 or 50 more chapters, at any given point if the author run out of ideas he can just throw them at the door of the final boss and end the story right there.
I miss cute goblins like these, too many became way too rape focused that a few stories I feel suffered for it, I forget names but they were fluffy series but then bring out the rape goblins so there's a bit of tonal whiplash.