RDNA2 (particularly, the narrower range from 6600 to 6800), is a huge step up in performance per watt. The lowest end one in there, 6600, is faster than a vega64 (which is much faster than rx580), yet uses less than half the power.

RDNA3's lower end chips, once they hit the market, are expected to further improve on this.

Most gamers won't upgrade to the current RDNA3 chips, because the current RDNA3 chips are top of the line, expensive, ~300w monsters.