I'm not sure of cracking a new market space would be a good idea either, just like how they aren't trying to go toe to toe with Allwinner offering H3 SOCs for $1ea with a quadcore and H.265 hardware decoding, it might not make sense to get into a 3 way war with Intel, Nvidia, etc.
Retaking or getting into another market with a single vendor or none presently would likely be more profitable, just as VIA did with their point of sale motherboards with crypto accelerators and tons of serial ports.
AMD only has so much money and talent, getting into a pissing contest is not something they are looking to do. Intel can piss harder and longer than them (just look at the contra-revenue they did with the HP Stream 7 and the $50 Walmart android tablet, Intel charged the manufacturer for the chip $X and paid them $X+Y for using said chip to compete with ARM).