If you think that's the case you're... well, not paying attention to late Millennial Nostalgia Culture. To give you a few shows that are very well remembered by later Millennials who grew up with them:
Codename: Kids Next Door (2001 - 2007)
Ed, Edd, and Eddy (1999 - 2009)
Rugrats (1991 - 2004)...