Are you having trouble with old-style rules too though? I feel that I can still absorb those fairly well.
I've experienced this as well, and put it down to age until I went back and played older (and complex) games with no problems at all. What I think has changed is the amount of "one off" rules designers are expecting gamers to take on board. "So and so communications network will go offline for seven game turns when side X does this."
Sometimes these special rules can amount to 20 pages and finding mnemonics to remember them is almost impossible. They are events not set in time (game turn three do this) but tied to actions (sometimes relatively minor actions) that start some event chain that can be pretty significant for the game.