I just pointed out Watchmen as a rare example where the producers took a big risk by making it about racism and violent extremism. Even though it was a superhero show, it felt fresh due to the new take and ideas.
It rankled a lot of feathers in the process, likely reinforcing Hollywood’s desire to continue making cookie cutter shows instead.
And about Harry Potter - it did a great job of evolving throughout the series to stay fresh. The kids grew up, learned new types of magic, and had constantly changing relationships for one thing.
Also, the series constantly introduced new and interesting characters or killed off extremely popular characters as well.
There was even an installment that heavily made use of time travel, which I thought was depicted in a really cool and satisfying way.