Aww I kinda like his bushy thick eyebrows, mainly cuz I have them too lol
Anyway, I guess even though Cedric is the perfect person to be Emperor, his apathy/reluctance to get into politics is his main flaw. By avoiding being involved in politics and reforming the kingdom, he is complicit in the suffering of the peasants, even though he does not directly partake in it. Tia is using her "marriage quests" as a way to show Cedric the corruption going on in the kingdom, and the result of being apathetic/reluctant to get involved into politics.
She ultimately wants Cedric to want to become Emperor, in his own right, not because it's part of the bargain.