Actually, historians argue about the level of impact da Vinci had on science, with many saying "not very much." This is because his notebooks were not published for centuries after his death. Most of his "scientific observations" were only to quench his personal curiosity.

In a sense, then, we can all still become da Vincis. Da Vinci was big on learning from experience, rather than by reading the works of others. Nothing is stopping a person alive today from observing nature and learning from it, in the same manner of Leonardo.

Will you be learning things that are already in a book somewhere? Most likely, yes, but I think that isn't really the point; the quest for knowledge may be more important than the acquistion of it.

Also, consider that many breakthroughs/innovations are from new entrants to a field# ie those who aren't experts in the new field. (Of course this may not apply to science as much as another field, but it's worth pondering regardless)

#See "The Medici Effect"