Saying it’s a matter of scale is an understatement. You need mass to keep the core molten, along with the right combination of elements to produce a working magnetic field that doesn’t fade over time. Mars has neither of those things going for it.

If you want to terraform Mars, you would have to rebuild it from scratch…basically creating a whole new planet with the right core composition and size. Even if you could pull all that material into one location and guide it all into a stable orbit, it would then take hundreds of millions of years to cool and set into something we could even hope to live on.

I don’t think human beings will ever be capable of that level of geoengineering. It’s just not realistic given the alternatives.