The engineering problem is insurmountable today. But there doesn't seem to be any reason it couldn't be done eventually, given our technological trajectory, unless we believe we are truly on the precipice of severe diminishing returns in most science and engineering fields, and I just don't see that right now.
George Cayley figured out how to build an airplane in 1799, but it wasn't for another century until materials science and high power-to-weight ratio engines made the Wright Flyer possible.
There are plenty of depths to plumb in space systems engineering that we haven't even really had a proper look at yet. A Mars mission with chemical propulsion is hard, but could be made substantially easier with nuclear thermal propulsion - something we know should work, given the successful test fires on the NERVA program back in the 60s. First stage reusability was fantasy 15 years ago, today it's routine.
Obviously, I'm extrapolating a long way out, and maybe at some point we'll run against an unexpected wall. But we'll never know until we get there.