Markets require trading partners to have any effect. It only concerns trade income.

Doctors do not "supposedly give "5% health bonus"". They give 10% health bonus. So what if they take the same time to create? Supplying a medical institution with the space, tools and materials it needs is not necessarily more time-consuming than creating a working sewer system. If you want to argue against the actual bonuses these buildings give, feel free to give logical or historical arguments.