This is a 100% subjective list of unpleasant situations I encountered due to frouzy board analysis before choosing my opening. I'm not talking about subtle suboptimalities, but obvious idiocies.
I am also aware that stronger players might never do these things, while weaker players will often do other terrific stuff. Feedback is very welcome, and I'd be happy to see your personal list of bad mistakes
10) Where did he get these goons?Ask the young witch or look at the second page.
9) I got all sorts of engine components ... why can't I draw my deck?
A village without +card, combined with a two-card-drawer, will never lead to a big hand, no matter how many you assemble. That also holds for hamlets and courtyards.
8 ) I managed to draw my deck, yeah. But where's the village for my three terminals?
Probably, one should think about it before taking that duchess with 5-2.
7) I'll go Big Money. I don't see any counter ... oops.
Beginners might overlook the problems BM faces, when there is a perpetual handsize attack. Stronger players will eventually ignore the danger coming from mediocre to bad cards, e.g. Noble Brigand, Knights or Pillage.
6) Reactions are generally weak.
Mostly, yes. This is why it's easy to miss strong openings with moat or trader.
5) You buy WHAT? That's insane.
"What do you want to do with all those hermits and native villages? And how did you get to level 40 with openings like beggar or woodcutter?"
Sometimes, opponents just play poorly. But in many situations, it's better to admit right from the start that you haven't seen their combo.
4) ... and why don't you care about those ruins and coppers I give to you?!
In general, junk attacks are strong. And so it might be, that you overestimate a looter, running into oppenents death cards, vineyards or scrying pools. Spamming coppers is questionable as well, if there are gardens, strong slogs, apothecaries, or even counting house.
3) Ah, a shelters game. Oh, many nice cards ... let's take a minute to analyse this board ...
... which is a good idea, unless you forget about shelters - and open with baron. Even ambassador is occasionally a bad choice because of shelters.
2) Now that I built my engine ... where's that f*$&ing +buy?
Hopefully, your engine can work without it. But if you need these double province moves to catch up, and there is not even an abandoned market you can buy for $16, you're in trouble.
1) Oooh ... there's also colonies!
It's really surprising how many players, including myself, repeatedly fall for this one.