It's absolutely insane to me how bad the user experience is with video nowadays, even video that's not encumbered by DRM or complex JavaScript clients.
The video experience for typical video files is great these days compared to the past. I think you may be viewing the past through rose colored glasses. For years it was a pain to deal with video because you had to navigate third party players (remember Real Player?), Flash plugins, and sketchy codec pack installs from adware infested download sites. If you were tech support for friends and family during that era, it was common to have to remove adware, spyware, and other unwanted programs after someone went down the rabbit home of trying to install software to watch some video they found.
The modern situation where your OS comes with software to play common files or you can install VLC and play anything is infinitely better than the past experience with local video.
Flash, also almost came built into every browser.
By the time both had gone away, HTML video built in was here. Of course, there were players like jwPlayer what played video fine.
Today, most browsers have most codecs.