You can do all of this without a PhD. I'd go a step further and say that a PhD is probably orthogonal to most if not all of these goals: 1. With PhD you drill

You can do all of this without a PhD. I'd go a step further and say that a PhD is probably orthogonal to most if not all of these goals: 1. With PhD you drill deep into a niche. By the time you're done, if a dozen people in the world care about your work, that's a success. Sure, you become an expert in this super-tiny niche, but the real world hardly swoons. 2. If you want to show your work so that other people read it, academic papers is not the way to go. So much so that the trend today is to encourage researchers to write easy-to-read blog posts that explain their work. 3. Expertise comes from solving problems, and that's not really what academia is about. You've mentioned ML, which is white hot right now but might not be in ten years' time. Most academic ML work competes on marginally improving on the same datasets, which rarely matter to real-world applications. If anything, what there is not nearly enough of is building quality data sets for new tasks. This is something anyone who trains themselves with decent statistics can get into. 4. Again, experts who monetise are experts that solve real-world problems. I don't know of successful consultant who are successful BECAUSE they have a PhD. 5. Writing books is a skill in its own right. I have a friend who's done a PhD and slaved on a book out of her thesis. She's very proud of it and all, but the volume we're talking here is a few dozens, bought by academic libraries. Is that your goal? 6. I feel the only people who invent something that ends up being valuable are those who apply their wits to real pain points. Most times, it's not the lone academic that launches a successful startup, it's the clever academic along with the sharp business buddy, and some seed funding. And even then, you still have to do all the legwork of any new business. A PhD, with its 4 years of being buried in the library, is hardly training for that sort of work. I think university is brilliant and curiosity is brilliant, and going out into the world and applying what you know to problems that you see can be incredibly rewarding. It's just that all this stuff doesn't necessitate a PhD.