If a cartridge is still in production, then it's not obsolete.
I think the .38 special is a perfectly adequate self-defense cartridge for a revolver. It isn't a big game cartridge to be sure but some would claim neither is a .357 magnum. Going on from there, some would say neither is a .44 magnum, now that larger cartridges are available for handguns but, again, some would say no handgun cartridge is adequate for large animals. But you are certainly more likely to be carrying a handgun around all the time instead of walking off and leaving it leaning against a tree fifty feet away while you're gathering an armload of wood.
Is it the best for self-defense? For a revolver, sometimes I think it is. I also think you're never poorly armed, given the basic limitations of a handgun to begin with, revolvers in particular.
Our expectations are not what they used to be.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.