You are correct in that superposition phenomenon is independent from entanglement! Nevertheless, In addition to supporting coherent superpositions, what makes

You are correct in that superposition phenomenon is independent from entanglement! Nevertheless, In addition to supporting coherent superpositions, what makes qubits powerful for information processing is the ability of coupling multiple qubits for creating entangled i.e., non-separable states. This property confers exponential complexity to a N-qubit system which can then encode and ultimately process 2^N bits of information simultaneously.