Being a developer for over 35 years I can tell you that generally it wasn't that much harder just different. I really don't think they were so much smarter, but you definitely had to be more resourceful. Most of the languages back then didn't have the rich libraries and frameworks available today and we had to work within much less available memory and disk resources. One of the pluses of that era was that your code HAD to be optimized or it just wouldn't work because of the memory limitations. I personally wrote apps in C, dBase, Clipper, and Microsoft Basic back in those days.
One advantage we have today that we didn't have back then is the instant ability to lookup a error message or search for a solution on sites like Stack Exchange. If you had a problem you were on your own for the most part. Needless to say, your library of books was quite large if you were a developer. Overall though we are so much better off today in my opinion. So many more choices and options and of course great communities like this one. :-)