Programming requires you to be able to think in a specific way, for some people this is easy, for some this is impossible (which is why in game development there tends to be a "hard" divide between programmers and artists... their brains are usually wired differently and they approach problems in completely different ways). So whether it's hard or not depends on how you think.
That said, if you didn't have any issues with assembly back in the day then probably that isn't the problem... Have you tried looking at doing it again? (homebrew?) If you still find it easy then maybe your issue is more with how things are handled now (I know a lot of people are good at low level programming but horrible at high level programming, and vice versa... I'm weird in that I can cope with both except the weird middle ground that's C++, which is why I tend to use C instead).
As to high level / low level I am more a low level c man
(I am a big almost religious fan of c language ;-) ) with respect to assembly or os internals too, but recently began to like javascript+canvas too, so i think I am not too low level or low level only
(in general I find myself moderately skilled and experienced now)
as to asembly
Back in the days I was coding in assembly far better than
today. :-/ A couple of months ago I was doing a couple of
procedures in nasm, some simple fpu/sse, and I can do
that, but it makes me far more trouble and less pleasure than back in the days (so it seem like I decreased in skills :/) :-?
Same with, when i was in high school i wrote some simple 3d
rasterizer in weak language qbasic and some code with models under that - I did it in a weekend or less time (about two days )
This year I have written some not perfect but of course
far better/faster software rasterizer in some proper c coding
but it cost me energy of couple of long weeks :-/
This seem to be strange and fatal :-/ - i got some wider
konwledge today and I still go forward but has much trouble with an energy to code. :C
I see it but am not sure how to do with that - still going
forward but it cost me much (but this is all digression,
I wanted not to speak about myself but maybe about some ideas why programming is hard situation)