You are equating "the left" with revolutionary communism - a common mistake, but still a mistake.
A substantial portion - I would even hazard to say, the majority - are not revolutionaries and do not seek a violent overthrow of the capitalist order. So what you are demanding of leftists here is to lie to themselves and others.
The actual faction within leftist politics that is actually in favor of violent revolution is a tiny fringe even within leftism, and the people who would actually be prepared to get up and start attacking governmental facilities or capitalist enterprises within a reasonable timeframe would be a tiny fringe among those.
As someone who considers themselves to be on the far left, I believe that you are correct in your assessment that a revolution would be neither practical nor feasible as is - and I would strongly argue the overwhelming majority of leftists, including most revolutionary leftists, would agree with you on this as well.
Sounds like your best bet is to let the military take over and run the place, then.
I think you are underestimating the ongoing loss of lives due to capitalism, as well as the loss of lives that we can expect in the not-too-distant future once our planet melts and we start shooting desperate immigrants at our borders.