get ublock origin, i hope you have that already, and add this to your My Filters page in the settings.
youtube.com##+js(set, yt.config_.EXPERIMENT_FLAGS.kevlar_watch_grid, false)
if you wanna go even farther, try youtube redux, it's another extension that lets you choose the past layouts over the years
thats all, have a nice day :3c
YouTube jumping on the Nostalgia bandwagon, by returning to the days of 2010-2014 when they screwed with the layout every other month. :v
