I'd say that some are easier and some are harder. It just depends on the car. I find that modern cars are way easier to diagnose and repair than older cars, even for non-professionals. Modifications are easier in my opinion as well. We have such a better understanding of technology today. Cars are built so systematically nowadays as well. Some people say that new cars are difficult to work on because everything is cramped and in the way, but things come apart way more easily than they did before. They can build a car in a couple of hours, and a well-trained technician can fully disassemble one just as quickly.