You could either go super traditional (never out of the top 100 in the last century)- so: James, Thomas, George, Charles, William, Edward.
Or uncommon traditional (so well known but not very popular at the moment - like Andrew) so: Peter, Phillip, John, Robert, Hugh, Nicholas, Laurence, Nathaniel, Jonathan, Mark etc.
Or try to meet in the middle with names that are classic and popular but that are outside top 10 currently: Samuel, Daniel, Jacob, Gabriel, Joseph, Joshua, Henry, Frederick, Benjamin, Matthew, David, Michael.
If you want to avoid true "middle aged man " names (for instance Andrew is more of a Dad name currently but is a classic/traditional name so will never truely go away) then just avoid names like Alan, Brian, Martin etc as they will likely take a while to return.