The good old days when the fish market was accessible to everyone and fish were swarming the aisles, but it wasn’t until tourists started to interfere that they were excluded from entering into the market.
But now we have Toyosu which is a different story and is the new fish market, more control over tourists who can watch back from behind glass, so basically closed doors to tourists and some obtain special access:
Toyosu Access: https://tokyocheapo.com/entertainment/sightseeing/toyosu-fish-market-what-to-know/
Tsukiji Market Calendar 2023: https://www.shijou.metro.tokyo.lg.jp/english/pdf/toyosu/businessdaycalendar2023.pdf
Tsukiji Today: https://blog.japanwondertravel.com/tsukiji-things-to-do-14775