>>9489>/a/ has probably deteriorated the least among the popular boardsYou're kidding right? Any lazy as fuck troll can derail threads there. Not to mention the /b/ tier "if ur waifu iz posted u must go 2 bed" and other shitty threads. Also the "you need to like what I like or you're just being contrarian" mentality that keeps leaking over from /v/. /v/, /a/ and /b/ are easily the three worst boards on the site. They're basically containment boards.
The only boards that are even remotely close to 4chan from even 10 years ago are /jp/ and /prog/ before it was deleted.