It obviously never became completely irrelevant. But I think programmers spend a lot less time thinking about memory than they used to. People used to do a lot of gymnastics and crazy optimizations to fit stuff into memory. I do quite a bit of embedded programming and most of the time it seems easier for me to simply upgrade the MCU and spend 10cents more (or whatever) than to make any crazy optimimzations. But of course there are still cases where it makes sense.