Why does the restored audio sometimes sound similar to the original?

Some restoration changes happen mostly in very high frequencies, so they may be subtle depending on your hearing, speakers, headphones, and the source file.

You can compare the spectrogram to see what changed. If the source already has enough high-frequency content, or if the problem is mostly bass, arrangement, mixing, or artifacts in the voice, a different tool may be more useful.

Try stem splitting, Neural Remix, EQ, Match EQ, or mastering depending on what you want to fix.