AMD got greedy and complacent with the 5000 series. High prices, no lower tier parts at all. And no decent APUs either.
I really don't know why they did that. It's not like you're going to get a budget gamer to spend way more than he wanted to, he will just go elsewhere.
Maybe they have a paranoia about being a lower end brand IDK.
Edit. As for E cores? IMO they are only there to make the power numbers at idle look better. If the fast cores didn't use so much power I doubt they would have even bothered with them. They're only there to bring back the idle power use and general day to day desktop power use.
With a 4/8 CPU it won't guzzle power any way, hence why they haven't use any E cores.