What is the ruling of the Sharia on delaying Jumu'ah prayer or not performing it in the mosque due to work circumstances that prevent a doctor from leaving?

The fear of not being allowed to leave for Jumu'ah prayer does not negate its obligation. Most of those who were sincere in their attempts managed to reconcile their work with attending Jumu'ah. However, if their repeated refusal is proven, and you are unable to find another job, then you would be excused. It is important to consider the ruling on residing in lands of disbelief (Kufr); it is not permissible except for one who can openly practice their religion, does not fear temptation (fitna), and whose residence serves a benefit, such as trade, medical treatment, or studying something that Muslims need, based on the Prophet's (peace be upon him) saying: "I am innocent of every Muslim who resides among the polytheists."