I use a mish mash of modern and old. I don't really have any strong preferences. I do prefer frames designed for 130/135mm, qr, threaded BB and ordinary straight 1 1/8.
I would say that disc brakes have grown on me immensely, particularly after this winters riding where my rim braked bikes gave in and only my drum/coaster/disc brakes could cut it. But disc brakes are hardly "modern" anymore.
I like modern geargroups quite a lot, I think the 1x wide range gearing biased towards the low end is pretty useful, simple to set up and just works. I also think clutched mechs are pretty neat, not that I really benefit from it that much due to my tame pensioner pace riding, but it keeps stuff nice and tight.