Slow down. We are both right and both wrong. Figuring out how the reasons apply to you is half the battle.

As a technical person you are better at getting it working so spending a couple weeks getting a working prototype is worth the effort, it might be ugly but it builds trust that it can work. If the idea is radical your potential investors/customers won't believe it is possible.

The real problem is until you have enough paying customers to pay everybody you are living on borrowed money. How you best borrow the money is the only question, and the answer if different for every situation. Some ideas are so obvious when seen that you can get millions from investors. Some ideas will get the "that ain't possible" reaction until you show them the finished product when they will beg you to take their money. Some ideas look cool but nobody is willing to actually pay for them. Some ideas are cool and will generate sales - but never enough to pay for all the people required to make the product. You have to figure out where you are.