Lenin cites this concept from Marx early in “State and Revolution.” To me, it implies that socialist states can be reformed from within to achieve communism, whereas under capitalism revolution is necessary to build socialism. I do not understand this at all. What makes post-capitalist society special in this respect? Am I misinterpreting something?
Note that thesis, antithesis and synthesis were never developed nor theorised by Hegel or Marx. Not only that, it oversimplifies dialectics into rigid structures.
AFAIK Hegel used other terms:
And while I generally agree with your take on rigid structures, I think it works better for a basic understanding of dialectics, it is worth noting also that for example the last step in a dialectical process can be the first step in another dialectical process.