AMD specifically stated, as of 2017, that they are not the "budget brand". The OEM desktop APU market is the last thing on their mind. They want to sell server CPUs to ODMs and OEMs more than anything else. You might think their console business contradicts that corporate strategy, but remember that the consoles/semi-custom business saved their bacon in 2015/2016 when they were on the rocks. The OEM APU market did them no favors back then. Yeah they're starting to get more serious about laptop APUs (it seems that Renoir awakened a great demand for that type of product), but desktop APUs? Not so much.
Everybody is capacity-constrained right now. Including Intel, once you realize that they only have a plethora of 14nm capacity due to not as many people wanting CPUs fabbed on that process.