One of my biggest pet-peeves is heavy emphasis on memorizing where enemies spawn. This is more of a problem with other shmups more than Touhou, but it happens in Touhou occasionally too. For example, EoSD stage 4, if you're not homing Reimu, and you forget when/where/how those spark-things spawn after the mid-boss (middle left, middle, far left, far right, middle, mid right, far right, far left IIRC)...You're pretty much forced to die or bomb unless you can dodge the books on lunatic with your eyes closed.
This is the biggest reason why I can't enjoy UFO as much as the other Touhou's. Because it is pretty important to remember where the UFO's spawn, what colors they are, etc. It wouldn't be so bad if I played one game and stuck with it for awhile, practiced it, etc. But I generally launch each Touhou like once a week, play a few times, then quit, so it's really a matter of personal taste for me than "bs" in a game.
Oddly spawning bullets I think are something everyone hates. Red Magic is a bad example IMO because they spawn directly behind the large bubble bullets. So you can predict how they'll spawn in advance, and if you can't, it's really your own fault. I find it more annoying how fast/suddenly fairies spawn near the top of the screen sometimes. I mean the whole "point of collection" thing is pretty unique to Touhou I think (only shmup I know that has one), so the player is encouraged to fly near the top of the screen sometimes, but sometimes those fairies just zoom out and own you. Almost every time I'm going for a first 1cc on a Touhou game, I only succeed after I get a basic grasp of when it's safe to fly to the poc in advance or not.
Shmups really are pretty mysterious. They really lull you into thinking that they require memorization less than pretty much any genre. And while it's indeed possible to excell at them via great skill without memorizing anything, it still helps alot more than you expect. Sometimes people claim a shmup is bs because it requires too much or whatever, and they quote another shmup which supposedly doesn't, but every time I try them, fact is they do and they really take for granted how much they play it without really thinking about it. Every little nuance like hanging on the left side of the screen before the enemies spawn there, to how to get a certain powerup/extralife/secret stage (memorizing 16 invisible bee point items in DDP PER STAGE for the secret stage? ugh), to starting off a stream-heavy attack on the far side instead of in the middle, they really add up into being massively important. So part of me feels like a hypocrite for not liking UFO'S emphasis on memorizing enemy spawnpoints/UFOs, but it's really the only reason that makes me fail to enjoy the game as much as the others.
Another Touhou subject of angst: Curvey lasers:
Do the experienced players actually read them so that they know where they will go when they are shot? Or is it just kind of a "twitch" thing as they get close for everyone?