Also, the nuclides result from sets of nuclear reactions in the stars, which can only produce some of them. The temperature far to cool to produce a set of nuclides according to equilibria. It's similar to chemical reactions at a reasonable temperature: the products depend on the reactants, the possible reactions, the catalysts and so on. Only a flame, thanks to its hot temperature, can completely reorganize the atoms and reach a simple equilibrium.
The situation is a bit different in a supernova with hotter conditions. Few years ago, astronomers told supernova made the elements heavier than iron, while fusion in the main sequence stars had to stop at iron or before. But such concepts may have changed meanwhile.