Some facts:
- Songs with high dynamic range have quieter and louder parts.
- Some songs are simply played louder than others
- There's a thing called "loudness wars" (I'll let you google for that) and these will always be perceived as being loud even at lower volume (which is the point even if it ruins dynamic range and generally speaking any song)
I quickly googled for that software and the link pointed to a YT video that is 11 years old. I'm a bleeding edge type of guy so, good luck :)
/edit
Forgot to mention, if DW Jukebox can't detect Replay Gain metadata from your files (assuming they have that data already) the only way to normalize is by editing the files...I'll let you google for normalization, compression and ... Audacity
Why don't you use something like foobar2000 (personal favourite), Media Monkey, MusicBee, etc, scan the library for replay gain, and call it a day?