Trying to keep my reasoning succinct in order to avoid writing a wall of text:
The soviets were geographically blocked from this being an option
Similarly for Vietnam for different reasons
Cuba doesn’t have the option of dedicating the requisite amount resources(and has the misfortune of being an island next to the most powerful current naval power)
China has the geography to become a great naval power. Sure, it doesn’t have both coasts. It has land connections that led to the Silk Road being a thing on the other, possibly a greater advantage.
They are building up militarily, and seem to be advancing commercial maritime pursuits on this well.
Thoughts?
The Soviet navy was more aimed at defense especially for their allies who were under threat of western invasion( They literally stopped the US from invading India because India was stopping genocide in east Pakistan). There was never too much point in building a navy comparable to marine powers like the US or the UK.
China didn't need a huge military fleet because tensions were not too high until a few years ago.
has been working towards minimising china's dependence on the west especially for military purposes so that's why they would probably aim to protect their own shipping lanes themselves.