There comes a time when you have to bow to physics...
Way before that point, we have to bow to pragmatism. There is a certain (relatively high) cost associated with carrying out such a project. There is, at the same time, zero tangible benefit if the project succeeds.
Ergo, there is no reason to "bow to physics" at all. Just concede to ourselves that interstellar travel by living beings simply isn't feasible without a major universe-opening propulsion breakthrough.
Basically: instead of examining the feasibility of building a giant stairway tall enough to reach the moon, you're probably better off waiting for someone to invent rockets.
Practical value? Well several-fold if you think going into space has ANY practical value. Firstly, it means spreading the human race
Accomplished by colonizing the moon and/or Mars, which is easier than interstellar travel.
Secondly: knowledge, we can gain knowledge through relays, and the network of machines.
Accomplished through probes, which are cheaper.
There are none in interstellar space. There are plenty in our own solar system that are cheaper to access.
Oh for three. Without some form of FTL travel, interstellar exploration is simply a dead-end. It's not worth the investment unless/until someone invents such a system and proves it to be functional.