Also in the last few years disk I/O optimization took a massive nosedive, especially under Windows. My 2013 laptop has a ~5400rpm HDD was so unusable with Windows 10 that even the login screen crossfade animation stuttered from disk I/O and updates took literally hours. Meanwhile Windows 8, released only a few years prior, was able to boot my older 2008 laptop from power on to desktop in ~22 seconds (i was so impressed at the time that i uploaded a video of the boot process [0]).
If you are used to the recent awful I/O performance it can be hard to imagine things not always being like that.
Besides you can also check a bunch of YouTube videos with old computers running Win95, here is a short one i found that goes through the bootup process and clicks around the OS for a bit.[1] The computer in the video is actually slower than the one i personally had too.