Technically you’re right

Time does move slightly slower at your feet than your head for example

And slower in denser regions of space than less dense ones

Also the simple discovery and creation of negative energy would do this

One problem is that for meaningful interstellar travel on traditional human lifetimes you need FTL. And FTL would require nearly a complete rework of the way we understand the universe

A lot has changed in the past 150 years but I doubt at this point we’ll rework the whole thing

I’m happy to be proven wrong tho

Dyson sphere highways, Antimatter, black holes that are tiny. Plenty of options to approach 99% light speed