I'm not going to undermine the relevance of JS in the history of PlayStation but they had a whole decade without releasing something worth of being called their best studio and they actually picked the worst time to not make something big because we are talking of the early 2010s, the moment in time where Sony was in the border of bankruptcy and then bounced back thanks to the PS4 and games that weren't from JS lol. The Last Guardian was kept alive in their worst economics in their history and when it finally released it was "ok".  

The people behind Astro Bot are still working in Astro Bot and the people who helped with Bloodborne did the exact same job that XDEV Japan is doing right now with ArcSys and has done with KT and KP, back up development and management. 

I love to talk about Housemarque but I don't see why this became a topic lol. If the reason is because it was part of the acquisition streak Sony did for this generations well that streak started with Insomniac and I'm pretty sure they are not going to close anytime soon lol so I say people should let SAROS do all the talk.

Asobi Team was part of Japan Studio, so even the last GOTY Sony had came out from it. Astro Bot is a Japan Studios IP.

Japan Studios struggled to have proper workflow to release games, indeed, but those games they co-developed were Demon's Souls and Bloodborne, some of the very best PS3 and PS4 games ever. Changed from King's Field to something that now in Elden Ring is one of the biggest games out there.

Locoroco they developed and Patapon they co-developed defined the PSP.

Gravity Rush is one most loved games on PS Vita too.

Currently losing a studio like Naughty Dog or Santa Monica would definitely be a bigger issue, sure, but Japan Studio was the very soul of Playstation.

PS1 and also best game ever, The Legend of Dragoon.

PS2 best game, Shadow of the Colossus.

PSP some of the most famous games, Loco Roco.

PS3 co-developed one of the best games, that spawned a sub-genre in gaming that is huge now, Demon's Souls.

PS4 the same, Bloodborne.

PSV had one of the best games too, Gravity Rush.

PS VR best games, Astro Bot Rescue Mission.

PS5 with Team Asobi following it gave us what is still the only PS5 GOTY so far, Astro Bot.

Ape Escape, Siren, Ico, Patapon, and so many more games.

Japan Studio was without a single doubt the best studio Sony ever had. Ever since the PS1 up until the PS5, even after most of the studio was disbanded, it marked pretty much every single system Sony ever had with some if not the best games there.