The left hand path, or the VamAchara, in tantra means the method, or the acharas in which the panchamakaras(5 M’s) is used. Namely Madira(wine), Mamsa(meat), Matsya(fish), Mudra(hand gestures?) and Maithuna(sexual intercourse).
These all are used not for pleasure, but for sadhana, although these things, all are related to pleasure and leisure, having more of a tamasic effect rather than sattvic or rajasic, which are considered better or ethical. Tamasic means made of the element Tamas, which means darkness. Left hand path, has had always been related to the path that rejects the authority, traditions and always thinking beyond the current rule of the place. People following this paths, have always had issues with kings or leaders, as these people wouldnt follow anything.
But for me, wine, meat and fish make sense if using for mental clarity and better ability of thinking. Meat and fish have vitamins and elements that helps improve our brain functions. For me, personally, a little amount of alcohol has helped to overcome my overthinking tendency and improving focus on things I wanted to focus. Meat and fish, do improve my body, and in some cases my cognition and thinking ability. The guru MatsyendraNath was following this path to understand the reality, which was later changed by Gorakhnath.