fwiw here's some tips from a working social scientist (i make smol theories about behavior and society and then actively test them) and teach others to do the same:
learn how to think systematically and scientifically: read up on methods and theory building in sociology & psychology (maybe philosophy too). then as you read the great leftist theories, try to apply your knowledge of methodology - see if you can trace how they're generating these theories. this will help you mimic this process without having to reinvent the wheel. most/all of the biggest names in left theory had at least a university-level education and were well-versed in systematic analysis and thinking.
practice those methods: start very small. come up with a specific problem first that you can easily define and see the boundary conditions of, and then generate a novel possible solution and/or explanation of why the problem is the way it is (i.e., hypothesis) based on what you've read from others.
learn how to be extremely critical of your own work: go through your solution/explanation in many iterations, being aware of what was generated from others' work and what you added and from where (eg, experience, empirical observation, intuition). Try to tear down your explanation/solution and break it apart: does it fully or partially explain the problem? what are plausible alternative explanations? (git gud at teasing out the possible from the probable, because not all possible explanations are equally likely).
Have others who are experts on the topic read your work and help you tear it apart (peer review). Ask them to write down their critiques so you can have record of the constructive conversation between you and can go back and think through the problem identification-solution generating process you built together
share it for the world to see and hope to god you're able to add even a small piece to an infinitely large conversation
Edit to add: keep in mind big theories take a looooong time to make; most professional thinkers, scientists and researchers never make contributions on the scale as large as the names we all know. the discovery and the contributions to practice along the way have to be reward enough
AWESOME
fwiw here's some tips from a working social scientist (i make smol theories about behavior and society and then actively test them) and teach others to do the same:
Edit to add: keep in mind big theories take a looooong time to make; most professional thinkers, scientists and researchers never make contributions on the scale as large as the names we all know. the discovery and the contributions to practice along the way have to be reward enough