I consider symmetry and polish to be a concern if they're graded "fair". "Good" is fine for naked eye purposes, and "very good" or "excellent" is just icing on the cake.
It all depends on how into cut you are. A "good" rating is equivalent to a Cadillac, a "very good" is equivalent to a Mercedes, and an "excellent" is equivalent to a Rolls Royce.
"Fair" is a Chevy, and "poor" is a Chevy that's been broadsided...
A diamond with Fair Polish/Symmetry will have Table/
Crown/Pavillion facets that are not aligned properly
thus minimizing light output and maximizing light
leakage. This may be the result of sloppy cutting but more
likely due to surface irregularities in the
diamond rough that make it difficult to cut and
polish in a symmetrical fashion. It also usually
is a warning of inclusions and or blemishes that
may reside at or break the surface which will
compromise the structural integrity of the stone.