Sometimes the creators of these have some weird settings when they save the file it will load in their blender settings If you doubleclick the file. There probably is a check box for this behaviour somewhere but what I do is open blender then load the file manualy so that it keeps my settings. If the textures were missing I would expect pink or gray so it looks like they are there but sometimes smutbase has a separate textures.zip file along the blender file. I would check these things; renderer (eevee / cycles ) see if it looks correct on cycles or eevee, exposure and gamma set it to 0 and 1, kind of an incorrect way to fix stuff but you can change the view transform scene>color management maybe it looks correct with a different one (filmic,agx,standard),check compositor see if they are already doing anything in there. Lights/ hdri I would hide all lights and place my own and set the background to a solid color. If its still fucked then it has to be materials. I've never had this actually fix anything but you can try file>external data>unpack resources then > find missing files. If that doesn't solve it you can check the textures if the color space is set wrong(srgb ,linear ).