5e Character Guides - why rate all features?

[Seramus]

Exactly what does it actually tell you if a Monk's unarmed defense is ranks as gold vs 2nd best blue vs 3rd best blue vs black on a guide? If one guide ranks the monk version as blue but ranks the barbarian's as gold or black, what does that actually tell you? I don't see that the color ranking actually provides real information.

It gives you additional data points to help determine what the guide writer considers valuable, so you can compare and contrast that with your own preferences.