Same here. I think it's more (for me) that other passions have overthrown games. I still enjoy gaming with others for the social aspect, but when I'm alone there are a thousand other things I'd rather be doing. I would say they don't make games engaging anymore, but really I think it's just that I'm not pulled in by them like I used to be. Age probably plays a bit of a factor in that, too.
I can go with that I think. I started off obsessed with the ruddy things, back when they first started, I even remember the first coin-op pong games followed by the simple breakout variants, and followed the progress through the arcade games, into the home computer games, though I ended up sticking with PC rather than consoles (always preferred mouse control in FP shoot-ups, much better in feel and control being analogue). Things like the first Elite, and Doom, XCOM games, Deus-Ex, etc etc. Nowadays I can rarely be bothered, and like your good self prefer other pastimes like reading much more.
It seems like the nearer they get to realistic, the less they appeal, and the less clever they are. When they had to treat the hardware like a precious resource, not to make more realistic as seems the case these days, but to overcome the limitations by coming up with an idea that's simple yet allows a beautiful pattern to be built from it, in an abstract fashion that doesn't deny it's origins by trying to pretend to be reality. The game as an abstract idea, implemented on a skeleton, that requires a purity of thought to overcome the technical limitations.
I go back and play a game of Doom and it's really a bit crap. But when it I first played it, it was something else, in a good way! But it made little allowance for realism. It was hung on a framework of a pure idea, and then 'painted' over to resemble enough reality for our brains to add this to our 'real' map of reality inside us that presents our world to us. It could become a part of that with ease. there were rules to link it to reality, but because they were so obviously artificial constructs, when they failed to work it didn't matter once we'd learn the game rules. For example, the 'world' in Doom was presented in a '3D' fashion optically. But it wasn't at all 3D, it was as 2D as it gets, but it exploited our own brains' workings to make it appear that way! And yet, once we'd played a level, most of us automatically realised this, allowed for it, and found the experience still very compelling, maybe because of that? It was in it's way, as absorbing and involving as many modern and far more sophisticated simulations of our world.
I think that the pure ingenuity that people had to come up with to overcome those failings of hardware were what the essence of these games was or where it lay, now we often look, with the big titles, at trying to recreate something that already exists instead, and this has stolen something vital from the genre, but I'm not sure I can express that more precisely. Maybe it's that the more it tries to recreate reality, the more my mind compares with reality, rather than an idea expressed as a fake reality, without compromise or intention to delude, and the more my mind finds the inconsistencies subconsciously unappealing?
Or maybe you're right, age alone may be a factor, and all the above is just trying to deny that?