For me personally, I found my GCSEs fairly straightforward and it was rather easy for me to get the grades I did get. But I wouldn't say that they were getting easier, they've changed which for some people may be easier, but for others it's not.
I did Triple Science for GCSE and some of the stuff covered in Biology and Chemistry was stuff that my parents and step-dad didn't really understand (quite interesting given they have degrees in Biomedical Science, Applied Biology and Biochemistry). They were helping me revise and tried to do one of the papers and would have got a lower grade than they did when they did GCSEs and O-Levels, so I just reckon that GCSEs are just different to how they used to be.