Well, the My Hero Academia manga has been published since 2014 and is still going strong. It's accumulated a substantial amount of content over the years, but the exact length keeps changing as new chapters come out.
I don't believe it's getting worse. The art style remains consistent, and the character development is still going strong. Maybe some people have different expectations, but overall, it's maintaining its quality.
First, focus on unique character development. Don't just follow the typical arcs of the canon characters. Give them new traits, fears, or goals. Second, create an original and engaging plot. Avoid rehashing the same battles and storylines from the original series. Third, use vivid descriptions. Paint a clear picture of the settings, like the bustling streets of Musutafu or the intense training grounds at U.A. High.
Making your 'My Hero Academia' fanfiction stand out can be achieved by creating a really engaging conflict. It could be a conflict that involves the entire hero society, not just individual heroes and villains. Also, add some depth to the relationships. Don't just have surface - level friendships or rivalries. Dig deeper into how characters truly feel about each other. For instance, how does All Might really feel about Midoriya in a more complex emotional sense? And of course, great descriptions of the action scenes are a plus.