My comment was meant to be serious although I personally believe that, depending on your age, you might be missing out on the real progress in those fields by just a few decades. As of today your goals are unfortunately in the science fiction territory more than actual science territory. Still, there are plenty of good career options available for you that will scratch that itch while providing a decent living.

Getting a PhD is not really about learning a lot in a particular field—it’s about contributing or demonstrating the ability to contribute to the research of that field. The process of getting a PhD involves or requires a lot of knowledge in some academic discipline, so it’s great if you are interested in learning about that area, but what you’ve researched—your dissertation (or equivalent)—is really what your PhD is.

As a PhD, I personally wouldn’t necessarily look down on someone with multiple PhDs, but I’d wonder why they chose to do that. Wanting knowledge from multiple areas is not a good reason because (1) you can learn things without getting a degree, (2) you could use multiple areas of knowledge to get a single PhD, and (3) you could do further research in an academic position, like postdoc or professor. Sadly, the third reason is easier said than done, but is not any easier with multiple PhDs—actually much harder—so why bother?

In my opinion, wanting to know about multiple fields is neither a bad thing nor particularly special. The trick is to have a life where you have the opportunities to do the research you want. What you get a PhD in should ideally be whatever helps you get on that path.

From what little I know from this thread, it sounds like you should be someone considering getting a PhD. My suggestion is to start looking at what graduate students and professors are working on. Try to start being a part of the academic world as soon as possible, which means independent research but also taking advantage of the academic community at your university.

As for what field you should study considering future technology and society, my opinion is to forget about all that. Definitely think about what you should avoid studying based on what the future holds (although I think those concerns are exaggerated), but don’t study something because it may be the next big thing. Study what you’re interested in and what can help you get the type of job and have the type of life you want.

Getting a PhD and working in academics is usually about slowly inching forward our theoretical understanding in an obscure corner of knowledge known to your small circle of a hundred or so fellow academics.

If that is not for you and you get more out of seeing your work affect the real world and/or building things you will see in use than advancing theory, may I recommend looking into engineering, computer/data science, or medicine (MD)? These fields are very flexible and you can lean into the more research oriented side and work in R&D as an engineer/computer scientist or in research/clinical trials as an MD, or even bring those skills fully to an academic setting where they are highly valuable. Additionally, you can much more easily pivot if your desires in life change.

PhD is a big commitment and I just would make sure you understand it is typically hyper focused on advancing very very specific, very niche knowledge that may not ever see real world application in your lifetime, so if you need that part for fulfillment, PhD might not be optimal for you. Coming from someone who spent many years in academics before becoming an R&D engineer at a company, which I love.

I can’t speak personally about the MD experience, but there’s an old saying about the difference in motivation between scientists and engineers which might be helpful:

Scientist: you build in order to learn things

Engineer: you learn in order to build things