All of the above, EXCEPT for the weird plots. The willingness to explore stories nobody else even thinks of is anime's greatest strength, in my opinion.
My biggest gripe of all are those little conventions all the shows follow like sheep. You know, the little things, like the massive sweat drip on people's heads, flailing their arms around when yelling, tomboyish girls always ALWAYS punching some guy in the face after they get falsely accused of being a pervert after the same tired old 'wrong place wrong time' bullshit.
-The professional team having one person say 'just a bit more' with another supposed professional saying 'that's too much' or 'it won't take it' only to be proven wrong every single time. Matter of fact any group of professionals regularly being surprised and generally acting like complete novices.
And the women. Don't get me started on the women. In most crap anime there's literally only about 5 types of women, and they all have gravity defying chests save for the little one who is impossibly perky and pretty much bases her entire life around harassing the main character. So many of the women in anime are eiher soft spoken eyes-closed-all-the-time cup hands in front of their chest types, or loud, brash tomboys that love beating guys up, because apparently that a joke that never gets old in anime land.
There is very little anime I like, but don't get me wrong- the anime I like, I usually love. My favourite film of all time is an anime and I'm never ashamed to say it, either. If the spectrum of anime could just get out of it's own asses just long enough to have a look at the diversity in the rest of the world's animation and realise how pigeonholed most of anime is, then maybe we'd start seeing all the tired old anime tricks start to disappear, or only appear where it's actually well handled.
You know, instead of the same old 'girl has just been called pretty-need to show a reaction-the anime text book tells us to make her look down, get red scribbles on her face, grab her own chest for reassurance of whatever, and say something very softly that equates to her not being worthy or some shit'. Oh, and there's a follow up entry here about then showing the guy, realising he's embarrassed her, sweat a massive single drop on the side of his head and then flail his arms around while trying to apologise for opening his mouth in the first place.
It's enough to make you want to puke.