What that being set! "being" a generalist is not for everyone.
There are some things to note:
1. Keeping up with all three is a LOT of work. Understanding the latest javascript libraries, deployment tech, UI tools and successful business models take a ton of time. I roughly spend 15-30 hrs a week trying new things our, designing or running spreadsheets not to mention the meetups and whatnot.
2. Every startup is looking for this person because they can enable so many parts of the success equation in one, self-contained shot. They add more value per square inch at critical phases of business growth that is a considerable asset. As a startup grows, this is personality turns into an optimal product lead, who can drive major decisions and participate in meaningful discussions with teams, investors and press.
3. Large corporations are not tuned to need or understand your services, unless you are accomplished in mid- to senior-level management positions.
4. You can visualize and eval business ideas quickly, then be able to communicate them to specialists with ease. I can't tell you the number of times being able to verbalized the need for a linked list or onHover whatever has made communcation easier with people who I bring to help me execute. This makes you a better implementer who is respected by counterparts and team members. Business folk quickly grasp CLV and burn margins when deciding to invest or advise.
4. You don't necessarily become an expert in everything. In fact, it's near impossible. I've had to focus of two or three major activities and fine tune my skills. This could mean I will be specializing in the future.
5. You don't get rest. The world is moving quickly, technology even faster. There are millions of able and hungry people willing to execute on their great ideas every single day. That means I have to keep moving or lose my flow. I can probably point to 7 or so ideas that were launched in the time I was evaluating the opportunity with 3 that have gone onto real growth.