I've heard quite a few people say that the conductor has an easy job waving his baton. Others have even questioned why a symphony orchestra needs a conductor. The best way to answer this question is to listen to music - a lot of it. Each conductor has a different interpretation of a musical score, which sometimes is very easy to hear. Case in point: these two interpretations of the Johann Strauss II polka "Unter Donner und Blitz" (Thunder and Lightning) by Carlos Kleiber and Herbert von Karajan.
Huge difference. One YouTuber observing the Kleiber performance writes, "You can see that ALL the work was done in rehearsal. All Kleiber has to do at the performance is inspire and keep time!" Whether the same can be said of Karajan or not, the point is that as a conductor rehearses with the orchestra, he shapes the piece. In performance, we see Kleiber inspiring the Bavarian State Orchestra along the way and even giving them a great giggle at the end. It seems like he was having the time of his life, and he probably was, but Kleiber worked hard during reheasals. Here is an example from 1970. It is a lot of fun to watch Kleiber conduct. I wish he made more recordings!
Karajan, in this performance with the Vienna Philharmonic, is not as fun. More often than not, he was a great interpreter of music, but the sound here is very austere and businesslike. There is a time for work and a time for play. Some conductors, like Fritz Reiner, were sadistically serious, whereas others like Sergiu Celibidache had a more humane, spiritual approach to music (and people). Whatever can be said of Kleiber or Karajan, they have both left a lasting mark on music. But Kleiber did it with a smile.