I largely agree with this. The ride isn't dated because the ride system itself and the associated thrill aspect are essentially timeless, and Splash represents the very best in class for rides of its type. The interior environment is also expertly themed to feel like a real cavern throughout.
However, I do feel like the characters and storyline may be entirely incidental to most guests' enjoyment, or I at least think folks here overestimate how central the majority of visitors feel they are to the overall experience. There might be more of an argument for the music, though.