I think you’re looking for the mythical “professional audio filter”, which, if it existed, would put all audio-engineers out of work.
There are levelator type filters, e.g., which will make the audio more uniformly loud.
It is also be possible to match the overall equalization to (approximately) match some reference.
DeEsser plugins are available to reduce sibilance, e.g., but they are designed to work on the vocal track in isolation, (without the musical instruments).
It would be possible to chain some of those processes together in Audacity, to automate remastering.