I think the issue isn't about how feasible the start up idea is in general, but how feasible it is for YOU. The comments may have been directing you to another

I think the issue isn't about how feasible the start up idea is in general, but how feasible it is for YOU. The comments may have been directing you to another idea for this reason. Using your example of Elon Musk, you can see even his start ups have a progression of ambition. That is, space travel and electric car companies are much less feasible than a payment system or news site. What is the difference between Musk and you today? Simple. Investors trust him with large sums of money since he has led successful companies before. There is a reason YC companies generally have low capital requirements. That is the lack of track record of the founders (and that business experience does matter). For your cable idea, the path towards that goal may very well be starting other companies first. Or be an industry insider who has the experience and connections to convince the incumbents to invest in you (like Pandora).