You wouldn't just leave a broken arm unset, would you? It's the same with a ship. Pieces of it were broken. Somebody fixes it. Broken things don't have to stay broken forever. That includes ships and people. It might be difficult, sure. People might say you've changed, but Theseus's ship was still sea-worthy for hundreds of years after his death. If it was change, if it truly was a different ship than the one that was falling to rot and ruin, then it was a change for the better.