(Even Disney has publicly recognized to their shareholders their mistake in backing the previous copyright extension act and have no further reason to back more extensions because they've proven the trademark and trade dress moat is plenty sufficient. Seriously, try to make a commercial Steamboat Willy derivative all you want without using Mickey characters or concepts from later shorts/movies/pop culture. Try to do it without violating Disney's long held trademark on Mickey's general head shape. Or to use a different huge empire's with a giant moat of properties, some of the earliest Batman stories just finally entered the public domain, but there's almost no way to commercially create a new Batman story without accidentally using later still copyrighted ideas/characters [early Batman used a gun, feels sometimes unrecognizable to modern expectations; most of his favorite rogues didn't show up for decades later] and without violating extensive trademarks on Bat emblems and the cowl shape, etc.)
Disney lobbied for copyright lengths and other protections because nobody else cared. And didn't ask for more over recent years because people cared.
You can do the same thing.
There are many neglected and unused regulations because markets never formed around them. Congress or a regulatory body thought they were doing something useful but werent.