Is the consensus of scholars not an argument against the general public, but only against them, and is it possible to adopt other opinions that contradict this consensus, such as considering interest on loans to be usury of surplus (riba al-fadl) and not usury of delay (riba al-nasi'ah)?

Giving attention to knowing the truth with its evidence is more befitting than following dissenting opinions and refuting them, for falsehood has no limit and objections to the Sharia are endless. The discourse mentioned in the question is flimsy, and here is a clarification of its general issues:

Firstly: Consensus (Ijma') is a legal proof and a fundamental principle of legislation. None but the people of misguidance disagree with it. We have explained its status and proofs in Fatwa No. 45513.

Secondly: Choosing between scholars' opinions based on whim and following their anomalies without considering the evidence is a blameworthy pursuit of concessions. Refer to Fatwa No. 32095.

Thirdly: Interest on debts (riba al-duyun) is unanimously and definitively prohibited. It is a form of Riba al-Nasi'a (usury of delay), and no one with intellect doubts this. Refer to the following fatwas: 143351, 120362, 56659, 69580.