I found the site looking up the word reactionary
the definition is essentially what you said. My question about the word is why does it have that definition.
It would seem that a Reactionary is someone who reacts. This is something we all do and reacting is neither bad or good and has nothing to do with what we have vs what we had.
It seems that reactionary, unlike revolutionary or visionary perhaps was coined with no regard for it's root. I know this is unlikely but none of the definitions I have seen tie the word to react.