I'm guessing the joke of this comic is that Arlecchino, Yelan, Clorinde and Sara synergize as a team? I haven't been paying much attention to the Spiral Abyss meta lately, I just know Arlecchino powercrept both Yoi and Tao, and Clorinde powercrept Raiden (but the other three are still perfect in-game).
That said, yes, Komachi should probably be here as well. She really fits the description. Perhaps she just couldn't be bothered to come pose for the photo?
I dunno, Komachi seems more like a 19-20 year old to me, with Shiki being 17. Not to mention Utusho looking 19 based on the vast majority of fanart. I used to comment on what age range the characters "seem" to be in. If there's anyone else who fits the Old Maiden's Alliance, it would be Mima and Shinki.
This post is referencing the collaboration Hololive did with the LA Dodgers on Friday (which also happened to be Shohei Ohtani's 30th birthday) and likely the food sold at Dodger Stadium.
I'm still having issues with posting assets in comments, but this is a reference to a scene from either Wreck-It Ralph or Ralph Breaks the Internet. It's that one meme with Calhoun and Felix together. I don't have an unedited screenshot, but this is what I was trying to post.