No, but we're talking about brute forcing billions of attempts per second, and we're not up against randomness, we're up against "the best pseudorandomness the

No, but we're talking about brute forcing billions of attempts per second, and we're not up against randomness, we're up against "the best pseudorandomness the human brain can muster", so the odds aren't 1 / <number of possibilities>. A password is severely weakened if it isn't sufficiently random.