No, a -1 penalty is still blundering away from an attack.
If someone who is paralyzed takes a -5, then you couldn't be blundering into an attack until your modifier somehow got to -6. Even a Dex penalty of -4 is still better at dodging something than a watermelon.
Someone with a Dex bonus is not completely motionless when caught flat-footed; he is simply limited to dodging as well as an average, Dex 10 commoner.
Someone with a Dex penalty (if we ignore PHB p8) is not completely motionless when caught flat-footed; he is simply limited to dodging as well as an average, Dex 10 commoner... except that he's not actually as good as an average, Dex 10 commoner on his best day, so the limit doesn't really affect him.
(If we take p8 into account, he actually gets better at dodging while unable to react to an attack.)
-Hyp.