I don't follow the "they wouldn't go from big screen back to small screen" logic in the case of this TV show which is itself a spinoff of one of the most lucrative cinematic franchises in history. Disney need content for Disney+, especially bankable SW content which has been virtually non-existent outside of The Mandalorian.

Rey taking the Skywalker name belongs at number 1 on this list. I understand what they were trying to do there... but come on, it's nonsense, and entitling the movie "The Rise Of Skywalker", ostensibly because of that final line, makes even less sense. This movie is also not a Skywalker saga movie in any real sense - an epilogue to it at best.

If a person lives their whole life with a drive or, more appropriately, a void they're trying to fill, why would they simply stop feeling that once one thing has been done to assuage it? It would be far less believable that something motivating Isildur since childhood would just "go away" the second he accomplished something.

But I don't agree with your core assumption this is justification for keeping the ring - Gondorians always harboured a belief they could use the Ring, and like Boromir, Isildur wanted to live up to his father and bloodline. Add to that the temptation the Ring works itself... for me this maternal drive is just a way to explain his character swerve from daft kid to god-killer.