Having a 'clear cut extraction plan' is all well and good if you're not out-manoeuvred by your opponent (or if they bend the rules) - they're not stupid, after all. They made the right choice not to try and fight their way out. To have done so would have been futile and could well have risked the lives of more of our servicemen.
Re our naval presence + posture in the Gulf, if it's any consolation to those who think we've been humiliated, even the US appears to be reluctant to get involved in a shooting war with Iran.