I've just gotten my internet restored after a month away (lightning strike, AT&T complete idiocy, 4 techs, new line, big ordeal), and re-subbed to WoW. That has a lot to do with my missing my awesome guildies and friends, and also missing the ease of it. I love lotro, but I love being able to just jump a griffon/wyvern and get where I need to be quickly and easily. On the other hand, when I'm in the mood for it, wandering around trying to find the next quest hub can be a lot of fun. But when I'm not in the mood for it, and just want to get some XP (I'd like to see 50 by the end of the year), very annoying and complicated.
On the other hand, I spent about 2 hours with a friend on facebook walking me through what I should be doing in WoW. I've been away since December, and lots had changed. I had almost full bags with no clue of what to do with any of it (still haven't tackled that) and no clue on where to go. Apparently the Isle of Thunder is my friend, and I did run through the first two scenarios to start unlocking it (which also helped me remember how the heck to shadow which is also on the complex side).
I also can't help wondering if I'd have as much trouble re-acclimating if I had a max level character in lotro. Jumping back onto the hunter or minstrel's fairly easy, but one's level 40 and one's 30. That's less than halfway to level cap, so there's far less for me to think about. I don't have bags stuffed full of transmog and cooking ingredients (and I have no clue what the heck I was doing with so many scallions), they're full of trophies, wood, random crafting things I'm saving for other toons (which go in shared storage till I wanna craft on that toon), and leather. The only complexity there is which task board I need to go to, and if it makes sense to send some of them to a lower level toon (to get more XP for the buck, so to speak).
Some of the simplicity of WoW has come as it's aged. I remember when you had to discover each flight point for each toon (which you still need to do in lotro), and when Azeroth was weird and new and I ran the length of a continent using only a speed boost in my early 20s (trick or treating all of Eastern Kingdoms) and alt+tabbing out to maps. I generally don't alt+tab out to maps in lotro unless I'm looking for something specific (ruin, quest location, that sort of thing); I can generally figure out how to get where I need to go. I like that about lotro (and I like the mithral coins option which allows you to go to any travel hub for one, just wish I got a few every month as a subber as they cost points).
I suspect part of it comes down to how I think about and play these two similar games so differently. In LotRO, the journey is the point. If I try to start power-leveling, I get frustrated because it feels so slow (the rested XP change doesn't help). In WoW, the socialization and end-game are the points, and thus I expect the journey to be fairly short (I have no idea what it will take to get Lyllea raid-ready, and honestly I'm not going to worry about it, I have enough RL stuff to deal with). If the journey is the point, I want a journey to be interesting, with nifty things to see and options for side-journeys, and I'm willing to forgive a certain amount of complexity for that. If the journey's a commute, I want simple and easy, preferably short, with as few traffic jams as possible.
I don't think one game is more complex than the other, I think they're just complex in different ways. That's good, it lets me enjoy them both, but I do wonder how much my viewpoint (very experienced former raider in Wow vs newbie with highest toon at 40) has to do with it.