I think it depends on multiple factors. There are still plenty of crappy PSU out there, but one thing that I suspect helped is better power management states for PCs. We used to see all the time, Athlon and Pentium 3 era motherboards and PSU caps fail but they often disabled halt idle or something to reduce PSU lag and associated instability, due to running CPU off 5V PSU rail with more current, and since then the industry moved to aggressive CPU and GPU voltage reduction and downclocking to save power, plus HDD capacity wasn't all that high back then, so many people needed multiple HDD powered to reach their target storage capacity.
PSUs had lower wattage ratings, but a higher average load long term, in addition to being less efficient themselves, plus I can't speak for everyone but as I got older I found fewer hours of time and less desire for long gaming sessions so reduced the load from that too, and don't push overclocking nearly as much because I no longer plan to upgrade every year or two, just want parts to last.
So... that hypothetical 300-400W PSU I had years ago, maybe had an average draw of 200W while today, usually higher than 400W PSU in a system but draw closer to 100W avg., or less for lesser used systems.
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