Wall Street is worried about Netflix's new shows. Its old ones are its secret weapon.

Netflix gets lots of attention for new seasons of hit series like "Bridgerton." But those shows aren't what drives most viewing on the service. Liam Daniel/Netflix Netflix may have a problem generating new massive hits. But massive new hits are only part of the Netflix story. Most viewing from Netflix actually comes from older shows and movies — a source of strength for the streamer. Wall Street worries that Netflix has an engagement problem. Netflix says it's doing fine, actually. Wall…