Younger, yes. At least the ones at the very top.
Tougher, no, not particularly. You can see photos of today's top riders equally covered in dirt towards the end of some of the Spring classics, if that is what you feel makes them look tough.
It used to be the case that most of the winners of the major races were in their late 20s or early 30s, while now they may well be 5+ years younger than that. But you also have to factor in much better sunscreen and medical care of the riders, meaning that in the old days, ridres would often look quite a bit older than their real age, while that doesn't happen as much now.