Spain (and the EU in general) has a lot of problems too, just different ones, and not readily visible to short-term visitors.
What are the Spain specific problems that will affect expats, Paul? We need the skeptics view!!
The bearish case for Spain is the poor economic environment that caused a modern-day diaspora 10 years ago. All of a sudden there were thousands of young Spaniards in the streets of London. The more affluent ones were being sent by their parents to study at a foreign university to improve their chances on the job market. The less affluent ones were doing whatever odd jobs the British economy would have them do because it was better than living with their parents at home.
https://en.wikipedia.org/wiki/Youth_unemployment_in_SpainThere's a reason everything is so cheap out there, it's because wages are low and professional development prospects are bleak. Can you name a large, innovative Spanish company? Didn't think so.
The next door neighbor France has simlar problems, but it's not as dire. Both countries have serious demographic problems that will require significant big sacrifices if their social model is to survive. But hey, at least they're not as screwed as Italy, the perennially broke peer.
Now the "good" news is that as an early retiree, you can fully insulate yourself. That's true stateside too: the opioid epidemic or Trump's latest stunt likely doesn't affect you at all if you're an upper middle class American.
Will Spain work for you? I don't know, probably? You have money, which is the ultimate cheat code everywhere in the world. But you're still part of the larger ecosystem, and that ecosystem is not healthy. That doesn't mean you shouldn't go, but don't fool yourself and only paint the picture you want to see. Find the local newspaper of the city you're targeting and read about what ails the locals.