Those mentioned by you are very specific kinds of meat, and there were doubts about how healthy they are long before the last century.

There is absolutely no evidence that any data about red meat or sausages also applies to other kinds of meat, e.g. those that have negligible content of myoglobin and saturated fat, like poultry breast or white fish.

I agree with what you said, that almost any study about vegan or vegetarian diets shows positive effects, but it is never clear which are the differences from the comparison diets that really mattered, because the compositional differences between diets were too many and too variable.