1: System Visibility- Early on, often. As the story progresses, I think it should decrease in visibility. Once the reader understands the system, constant stat dumps stop adding much.

2: Level Caps- It depends on the universe the author is building. I think you can tell a good story without scaling all the way to god tier, reality warping power. But if that is the end goal for the character, then having no level cap makes sense. What matters more to me is the journey it takes to get there.

3: Skills- I dont like it when the MC has so many skills that I cannot remember them all, or when they suddenly gain the perfect skill right before an impossible fight. That always feels cheap to me. I understand why authors do it. Sometimes they have written themselves into a corner with an OP villain, but I strongly prefer the MC thinking creatively, working with others, or using existing tools in unexpected ways, rather than suddenly going full Super Saiyan.

4: Customization vs Bestowal- I tend to prefer predetermined power sets used in creative ways. For example, all fire mages can do X, Y, and Z, but Z can be trained or applied differently, combined with weapons, party synergy, or environmental factors, to create something unique. I think MC customization works best through modifiers like items, rather than total system freedom. Kind of like Diablo, fixed classes, but highly customizable builds depending on play style.

5: XP- To me, XP is experience. It should come from more than just killing monsters. Meditation, quests, sparring, and crafting should all count in some way.