You're coming off fairly condescending. Leftists of many stripes not only have thorough critiques of Capitalism, but offer a wide range of solutions, both legislative and grass-roots.
There may be a lot of ranting, but most of it is based within robust theory and legislative efforts.
Strengthening unions and workers rights laws is almost always advocated for. Weakening the ability for corporations to exploit their workers and the general population/environment is another.
I'm an Agorist, that means I advocate fighting Capitalism from the ground up using grey and black markets to subvert existing Capitalist structures.
So acquiring and distributing pirated materials like college textbooks and otherwise expensive software is one example. Helping people jailbreak/hack their devices to run unofficial software that the corporations don't approve of is another.
There's lots of information out there, don't mistake memes and ranting for empty idealism.