Generally I agree with your critique of this approach to a subject, but I think philosophy is an exceptional case, more like a hybrid of mathematics and literature than something like physics.

If philosophy was taught the same way physics is, it would be utterly intractable.

Unlike physics, philosophy has little in the way of settled canon. There are precious few bits of established gained ground when it comes to the truly fundamental questions of a given area of philosophy.

At an entry level, the point of a proper philosophy education is to foster an appreciation for the big questions and for critical thinking.

From there, it is convenient to work historically as it provides both a natural progression of thinking on the topics as well as perfect training for how to find holes in arguments.

By begining with Socrates, the student is exposed to robust and relatively accessible arguments on most of the major topics in philosophy.

This helps students approach the questions earnestly.

Trying to begin with an examination of the current thinking on most philosophical topics would be almost impossibly divorced from that which a new entrant to philosophical thinking could grasp in a deep and rewarding way.

Instead, a good philosophy teacher can walk a student through a rewarding exploration of the major topics in philosophy across history, showing how the implausibilities of the past are far more robust than most think and how much of our present intuition is on far shakier ground than most think.