Loudness war was increasing amounts of compression.
The opposite of compression is expansion.
Here are 3 free expander plugins which work in Audacity on Windows …
La Petite excite … [Free] [VST/AU plugin] La Petite Excite [says “exciter”, but it’s a (2 band) expander ].
ToneBooster’s FIX … Free (v3) ToneBooster's plugins - #2 by Trebor (6 band)
Steve’s dynamic mirror … Envelope follower / ducker - #6 by Trebor (1 band)