I might be raising measurement problem in quantum physics in different words, but I will ask the question.
Quantum decoherence has been proposed by proponents as a theory that eliminates all weird issues involving quantum mechanics, such as Schrodinger's cats and measurement problem.
So in quantum decoherence theory, system (example: a particle) becomes "measurable" when system interacts with another system or environment with certain conditions and consequences.
But this seems to raise issues of how systems can ever be interacting "objectively". After all, every system described by wavefunctions that only give probability for possible measurements in general (of course there are cases that when met with proper basis and knowledge of wavefunction, definitive measurement can be guaranteed). This for me seems to suggest even before quantum decoherence, two systems that will interact have been connected by some wavefunction that describes the chance of quantum decoherence. Or we need some kinds of observers to either bring effects of quantum decoherence.
If the question seems a bit confusing, the context in which the question is being asked is how quantum decoherence theory affects quantum mechanics's measurement problem.