They are subjective even in the classical, nonrelativistic mechanics of a pendulum, since the notions appear when you try to relate the theory to a real pendulum. In classical, nonrelativistic mechanics, the interpretation of the words ''observation'', ''experiment'' and ''measurement'' needed to build a proper bridge between classical theory and reality are also subjective. (The respective definitions in the wikipedia pages linked to contain many unexplained words whose meaning is as subjective as those of the above two words, or even more.)But the usual interpretations of "uncertainty" and "approximately" are subjective.
So why do you regard classical, nonrelativistic few-particle mechanics as philosophically sound, but complain about foundational problems in quantum mechanics?