  Magnetism in two-dimensional (2D) materials has attracted considerable
attention recently for both fundamental understanding of magnetism and their
tunability towards device applications. The isostructural Fe$_3$GeTe$_2$ and
Fe$_3$GaTe$_2$ are two members of the Fe-based van der Waals (vdW) ferromagnet
family, but exhibit very different Curie temperatures (T$_C$) of 210 K and 360
K, respectively. Here, by using angle-resolved photoemission spectroscopy and
density functional theory, we systematically compare the electronic structures
of the two compounds. Qualitative similarities in the Fermi surface can be
found between the two compounds, with expanded hole pockets in Fe$_3$GaTe$_2$
suggesting additional hole carriers compared to Fe$_3$GeTe$_2$. Interestingly,
we observe no band shift in Fe$_3$GaTe$_2$ across its T$_C$ of 360 K, compared
to a small shift in Fe$_3$GeTe$_2$ across its T$_C$ of 210 K. The weak
temperature-dependent evolution strongly deviates from the expectations of an
itinerant Stoner mechanism. Our results suggest that itinerant electrons have
minimal contributions to the enhancement of T$_C$ in Fe$_3$GaTe$_2$ compared to
Fe$_3$GeTe$_2$, and that the nature of ferromagnetism in these Fe-based vdW
ferromagnets must be understood with considerations of the electron
correlations.
