Keynesian economics is a relic of the past. It worked in the past when the profitability of western economies was much higher. However, the rapid accumulation of capital during the Keynesian period also tanked western profitability, leading them straight into neoliberalism.

Keynesian economics feels more left to us today because social democrats want a return to keynesianism. In the same way, there are elements of feudalism that may seem "left-wing" to us today, such as the fact that peasants got more days off and took better care of the environment.

Keynesianism is not left-wing though. It was supported in the past by conservatives because it advanced the interests of capital. Keynesianism created an economy in which capitalists could grow very wealthy very quickly, and the western imperialists could accumulate large quantities of advanced weapons. That period however, is over. What advances the interests of capital today is different from what advanced them in the past. So conservatives have changed.