Metro
The metro makes it easy to combine moods: historical quarters, green spaces, modern areas and smaller routes through side streets.
Paris
Paris by metro & bus
Anyone who wants to experience Paris consciously rather than just quickly should use not only walking, but also the metro and the city bus. The metro helps with rhythm; the bus helps with perspective.
To me, that is not a fallback solution but a genuine way of composing future Paris days.
Bus
Some bus lines become small sightseeing routes in their own right. Line 72 along the Seine is a strong example, but the wider point is to see Paris as a sequence of views rather than only as a transfer problem.
Day tickets
For days with repeated stops and re-boarding, a day ticket often makes more sense than thinking only in single rides.
A personal toolkit
The more often I am in Paris, the clearer it becomes that the city does not ask for a fixed order. Metro and bus help combine parks, streets, history and modern life according to mood.