Agree with this, but it is possible to make it as light. Does come at a cost and some trade offs.An AR-10 in that weight class requires some fairly exotic parts, and a pencil profile barrel. IMO a pencil profile barrel on an AR-10 kind of defeats the purpose.
I know, because I just built one with a xanthos receiver set, JP LMOS bolt, all titanium V7 bits and magnesium handguard, smoke composites stock set, etc etc, and it still clocked in at 7lbs with a 20” proof CF barrel in 6.5 CM.