There is a plot to the John Wick movies, it's just not very deep. The plot can largely be summarised as "Wick was an assassin, but gave it up because his wife died, then some Bad People killed his dog. Wick is very upset by that, and will now express that via the medium of choreographed fight scenes". Also, there's a whole assassin sub-culture, which is wonderfully executed, if completely mad.

Overall the plot doesn't really make any sense, but it also doesn't need to, it's just a hook on which to hang some spectacular set pieces.