I'm sure it would have been more convenient and practical for John Alcock and Arthur Brown to have an INS system on board their Vickers Vimy and a pair of Garrett turboprops out on the wings instead of two WW1-vintage Rolls Royce Eagles; but they did not have all that, and this, among other reasons, and skill required to fly such a flight with what they had, is why their transatlantic flight was remarkable. Likewise, the skills required to drive a 737 around the sky without and FMC or INS, is why most people want a 737 of 1960s vintage, since they already have one with modern avionics.
Skill of navigation is just a part of flight operation, not everything. Beside letting VOR/DME takes most of my attentions during the descent I'd rather spend them on the energy management and perform a smooth descent.
The art of flying vintage won't disappear by just adding an INS or GPS. Just like adding a GPS or INS to those Russian aircraft. It won't take away the spirit, we can see them on tu154 and even Yak42. I have no idea why my words lead you to think of flying a FMC equipped add-on.