I kind of disagree - many paintings are actually better experienced on print or online than in real life. Just take your example of Mona Lisa - you will get a better impression of the art from a good reproduction than from watching it behind glass surrounded by hordes of tourists at the Louvre. It is a relatively small painting and you can't even get close! Many classic paintings are awkwardly placed with bad lighting and so on. Some museums hang paintings in multiple rows, so you have to be a giraffe to enjoy half of them. Digitalization on the other hand is typically done under perfect light and viewing conditions.
In any case, for most ordinary people it is totally unrealistic to travel to museums all over the world to enjoy the real paintings.
In any case, for most ordinary people it is totally unrealistic to travel to museums all over the world to enjoy the real paintings.