Sasuke doesn’t use Susanoo to replace his arm for the same reason he doesn’t use any other means to replace his arm. He believes that his missing limb is part of his atonement for the pain and suffering he caused. It’s also probably used by the author as a reminder of all of the things that happened before.
Who are Rock Lee’s parents? It’s a Naruto mystery, as there’s no canon information about their identities or backgrounds in the series.
Ultimately, Guts and Griffith haven’t killed each other in either anime adaptation because such a confrontation has not yet happened in the manga, which is the original source material. The manga has run irregularly for decades, and events in 2021 caused it to stop production for a full year.
The animation changed from Naruto to the sequel, Naruto Shippuden, largely because the budget increased and the studio was determined to raise quality. Even so, you can see quality discrepancies comparing episodes only in Shippuden, and that is largely due to varying budgets and production times per episode.
One Piece has been on the air for more than 20 years. The graphics steadily improved over the course of that time. That said, there are two very noticeable changes in the animation style. The first happened in 2007 when the studio started wide-format and HD production.
The second was after the well-known time skip.