Can a mechanical engineer make anything they dream about

While there are the limits of physics and what we can build today in general if you can come up with an idea engineers can find a way to build it. With the advent of 3D printers it is becoming easier and cheaper to build literally anything.

You are limited by the laws of physics, but not by your own limitations. Engineering is a very collaborative profession. You can bridge your lack of technical capability by working with others that are skillful in that area.

The interesting thing for me is when I find new ways to apply physics to solve a technical problem. I even impressed a professor with a focus on magnetics with a product that used a magnet floating in its own flux field.