  The study of $J/\psi$ photoproduction at low energies has consequences for
the understanding of multiple aspects of nonperturbative QCD, ranging from
mechanical properties of the proton, to the binding inside nuclei, and the
existence of hidden-charm pentaquarks. Factorization of the photon-$c \bar c$
and nucleon dynamics or Vector Meson Dominance are often invoked to justify
these studies. Alternatively, open charm intermediate states have been proposed
as the dominant mechanism underlying $J/\psi$ photoproduction. As the latter
violates this factorization, it is important to estimate the relevance of such
contributions. We analyse the latest differential and integrated
photoproduction cross sections from the GlueX and $J/\psi$-007 experiments. We
show that the data can be adequately described by a small number of partial
waves, which we parameterize with generic models enforcing low-energy
unitarity. The results suggest a nonnegligible contribution from open charm
intermediate states. Furthermore, most of the models present an elastic
scattering length incompatible with previous extractions based on Vector Meson
Dominance, and thus call into question its applicability to heavy mesons. Our
results indicate a wide array of physics possibilities that are compatible with
present data and need to be disentangled.
