I agree that outside of their special scenes the unique characters seem bland.
After the loan is paid off there is still the civil war arc and the forest and beasts arc, both of which require a lot of MC involvement with several objectives.
Yeah, there are a lot of quests to do, but they're mostly battle, conversation, or fetch quests. One can simply spam time to get everything, including EXP, and do the quests easily. There's no pressure like there was with the loan quest, the game becomes trivial. I know many dislike the Loan and just want the characters, but I would still like to see a quest like the Loan in Arcs I and II in Hard Mode. For me, having to pay my debts while also leveling up and doing quests was the best part of the game, it was a fun challenge (then again, I think the challenge being restricted to hard mode was a good idea and new Loan like quests should also be limited to harm mode).