I have been designing electronic cards for more than 40 years. Some of these were attempts to make new products, never existed before, others were just smaller, cheaper, smarter or safer versions of existing circuits. Not all of them were successful, but those that were, helped my customers to create handsome profits. I made all these projects under strict NDAs, so I can tell very little about them here...
I loved low level FW development and I was very good at using cheap 8-bit microcontrollers in places where nobody considered using them, but I see that the future is specialization. Designing PCBs is the area I know best, and because I do it all the time, I can do it faster and in better quality than those who are less specialized.