I think part of the problem is just that mastery is currently capped. There are plenty of people who main or even one-trick a champion, but they usually have to announce how much time they've spent on that champion independently of their mastery rating, because past a certain point they cap out and the grade doesn't adequately describe how committed they are. I don't think many people really care about the title each grade awards, and the crafting requirements for 6 and 7 are largely seen as obstructive and not entirely dependent on skill or commitment. In this respect, just doing away with those obstacles at higher grades, doing away with titles, and just uncapping mastery would allow players to truly show just how much time and work they've put into their favorite champions.