The conductors either support the flow of majority carriers or they don’t but they are unable to demonstrate diversified properties under diversified varying conditions, unlike semiconductors.
Actually, the conduction of current is limited and determined by the flow of majority as well as minority charge carriers in semiconductors whereas the conduction of current in conductors is mainly focussed upon as an interconnect.
Just think of an example where you can use a metal for demonstrating rectifying properties or design a device with conductors only that can amplify. If you can, you will surely get a huge prize because no one has ever had.
Further, in an era of downscaling, the device sizes are getting reduced successively and I would like to note one thing that in this era, the interconnects constitute of a major area in an integrated circuit. This is another problem.
Let’s take a very simple example that can be easily understood. You try to design a 2-input AND gate using conductors only. You put push buttons for inputs and you sense output at the center of these two conductors ( I could think of this configuration only at this moment. You can model it in different styles and cross-check your results). The circuit will always be either open or driven by the stronger supply, then the logic of the circuit fails. Similarly, analog processing can also be done with the help of semiconductors using conductors as a part of interconnects only.
The industry is progressing towards better and advanced engineered materials and devices – domains of magneto-electronics, spintronics, etc. that can give better results than the elemental and basic semiconductors.