Possible, but the stuff we’re talking about is recent, GTAV took 5 years to make, Final Fantasy XV has been in development for about 10 years and isn’t out yet. While tools get more capable all the time, think about drawing or sculpting, still takes a ton of time even with advancements in technology and mankind has had those things for a very long time. The project you want to do has both technical issues in terms of making something that big that functions, but also in how much content you would have to make which simply takes time.
It’s also probably an issue to plan a lifetime project on a piece of software, since it’s going to be replaced and become obsolete at some point, which would require you to either move to a newer engine or try to keep using the old one.
You could still accomplish a very impressive project if you break it down into something more reasonable. People have done some pretty incredible projects, but it’s always something that’s actually possible.