At some point PBR (physically based rendering) was introduced into FSO, which changed the reflective lighting from either based on sort of reflect or other type of maps to based on a separate roughness/metallicity texture, or something along the lines - I have no idea how it works in detail
. What's important is that it lets models with properly crafted PBR maps to look much much better, while it doesn't really look as good for models without them. So one problem might be that you're playing with models without PBR maps which are still very numerous in MediaVPs.
On the other hand, a different complaint might be that lighting itself is dull and without variance, that's because FSO currently has got extremely high ambient lighting in the default lighting settings. I suggest trying out some lighting settings that might fix this. Some presets are here https://wiki.hard-light.net/index.php/Sample_Lighting_Settings
and if you want to try and experiment with values, see explanations of the flags here https://wiki.hard-light.net/index.php/Command-Line_Reference#Lighting
Watch out for -no_emissive_lighting and -emissive_lighting. The former is used in builds roughly before 19.0.0-RC2 (including 3.7.X, 3.8.X and 19.0.0-RC1) and it disables emissive lighting (which is on by default), while the latter is used in builds starting from the mentioned RC2 because there emissive lighting is off by default. I suggest forcing emissive lighting to off and having shadows turned on too for cool looks.
My personal setup is -ambient_factor 73 -spec_point 0.3 -spec_static 1.0 -spec_tube 0.4 -bloom_intensity 45 (with emissive lighting off).
Also note that you can experiment with lighting settings on the go - without relaunching FSO - in the Lab. Just press F3 in the main menu, select a ship and a background and try out some checkboxes and sliders. This lets you look at your ship of choice with the background of every mission available.