I'm really not convinced there's been that much change over the decades, certainly on some airlines. That opinion is based on > 30 years of being legitimately able to walk the length of Long Haul aircraft as part of the day job and so actually seeing what passengers get up to.
Certainly where I was we carried a high number (maybe >25% of total on board) of passengers off connecting flights and once the first meal service was done you'd expect to see a high percentage of seats reclined, day or night,.even in the '80s and certainly through to the 2020s..and frankly be it 1995 or 2025 if you told passengers on most breakfast time London to JFK/BOS/IAD etc etc flights they couldn't recline because "it's morning and it's daylight" you'd have a riot..
What has changed is seat pitch (point made by @Poppins21 ) but also there seem to be more leisure long haulers, some quite vocal, who pitch up at the airport fresh as a daisy, don't understand why anyone should recline and are completely unwilling to try Chairman Mao's idea of contemplating walking any distance in other passenger's shoes...so.the grumbles start about "it's morning,.how can anyone be tired"..etc etc.
It's a recipe for conflict....