Add back your material exclusion directories. You've removed them all somehow which can cause the material browser to crash from loading so many items, such as UI icons and model materials
Either check you're using the tf.fgd instead of hl2.fgd/etc, or manually add in the exclusion directories to your FGD/hammer
Here's what I use, it's nearly identical to the default
@MaterialExclusion
[
// Names of the sub-directories we don't want to load materials from, as they are useless
"ambulance"
"backpack"
"cable"
"console"
"customcubemaps"
"cubemaps"
"debug"
"detail"
"editor-ficool2"
"engine"
"matsys_regressiontest"
"hlmv"
"hud"
"logo"
"maps"
"models"
"overviews"
"perftest"
"scripted"
"shadertest"
"vgui"
"voice"
"vr"
]
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