But since H.G. Wells’ The Time Machine was about a machine, it ruined everything.

If you’re going to see a machine operating, you’re going to think about how it works, and that’s not good for movies. This means the writer, director, and production designer all start making a lot of guesses about science, depending on what cool shit they want to show you. This leads to questions you have to answer:

Is your protagonist transported to the same fixed point in the universe at a different time, which would mean after the time jump you would probably be somewhere in empty space, or is that problem just tossed out the window? Is your time machine a piloted contraption, or does it create a portal, or can it perhaps be worn on the body? Does the machine accelerate time around you, or beam you through a portal? If it accelerates time around you, do bystanders see it just sitting there for perhaps hundreds of years?