I'm not sure that the earliest iteration of GCSEs were "easy", though - we had to do calculus, for example, which I believe isn't taught until A level now.
The thing is, for everyone sitting them, they are the hardest exams they've ever done, so in that sense, it doesn't particularly matter if the material included is "easier" as it isn't for that cohort
Likewise, there's a reason that Science degrees switched to being 4 years "Master" level - students were coming in lacking the fundamental learning that enabled people originally to get through the material to reach graduate level in 3 years. Obviously, there'd have been an outcry if people were expected to study for a further year for the same qualification, hence the rise of the undergraduate master's. (At least, according to the Science dons and academics I know) It doesn't mean, though, that A levels are objectively easier, necessarily, because the students have been taught different material.
I don't think the pressure has increased - admittedly, I went to an extremely academic school, but everyone took at least 12 GCSEs and 3-5 A levels. We sat unseen exams in every subject every term from the age of 4, and grades were read out to the whole year group, although we were also streamed on ability. It's quite a useful lesson, to be honest, that no one comes top of everything/all the time, good preparation for how university was in those days, based on three hour unseen exams (it was actually easier in that sense than A levels, where you had at least 3 3 hour exams per subject) - but again, we knew no different.
I am not sure, as a result, how helpful it is comparing generations in this way, as it's not really like with like, especially as there are so many additional variables.