Charmonium decays provide a gluon-rich environment, making them one of the most promising hunting grounds for light QCD exotics states with gluonic excitations, such as glueballs and hybrids. Using the world's largest samples of $J/\psi$ and $\psi(3686)$ events produced in $e^{+}e^{-}$ annihilation, the BESIII experiment is uniquely positioned to study light hadrons in charmonium decays. This proceeding highlights recent advancements in the study of $1^{-+}$ states and glueballs.