This seems true, but
this article shows how the Cubs uniforms have actually gone through some pretty odd changes through the years and how they are now actually very unique.
Some highlights:
-The Cubs are the only team to use a felt applique for the logo on their helmets. That's why it pops out off of the helmet.
Pic
-The Cubs are the only team in any major professional sports league to have the TM or R symbol on the logo on their uniforms.
Pic
-The Cubs are the only team to wear the National League patch on any of their uniforms. They wear it on the alternate blues. No team wears the American League patch, either.
Pic
-The Cubs red "C" surrounded by a blue circle is actually borrowed/stolen from the Chicago Athletic Association, which William Wrigley had ties to.
The Cubs uniforms have been pretty steadily similar lately, but their history is pretty diverse. From pullovers to powder blue, it's not like they're the Yankees.