For Keine's midboss spell, killing familiars helps a lot. With Youmu and Marisa you have to do some risky high speed micrododging for a moment, but it's worth it because it really reduces the bullet density for the rest of the spell. Youmu's even better because she can then switch to the slow Yuyuko, and low speeds obviously make micrododging easier. With Scarlet team, Sakuya can't kill the familiars quickly enough to make a difference, and Remilia is so fast, it's basically risky high speed micrododging for the entire spell.
For Keine's 2nd and final spells, Youmu (and I'd assume Marisa) can kill at least 1 of the familiars before any bullets ever even reach them, which again makes things less dense for the rest of the pattern. Sakuya, once again, can't kill the familiars quickly enough, so the high speed Remilia has to dodge a greater number of bullets.
Maybe it's just because I'm not used to fighting her with the Scarlets (I usually use the 9 stages patch, so I still fight her often with the Ghost and Border teams). But I have a hard time staying under Reimu and dodging her walls if I stay focused for her nonspells. It's noticeable on her 1st spell, but it's really noticeable on her 4th. In fact, I thought that was the whole point of the familiars in her 4th. In the third she shoots walls at you, you go unfocused, jump to the other side of the screen, focus to dodge the leftover amulets and deal more damage. In the fourth you can't play unfocused because of the yin yangs. Unless you have a shot type that can kill them quickly.
I feel like I'm repeating myself here, but in Reisen's 2nd non, Youmu and Marisa can at least kill one of the familiars before too many bullets reach them, which makes the pattern less dense, then Youmu can switch to Yuyuko which makes micrododging easier. Sakuya can't kill the familiars quickly, so you either have to play unfocused for a long time trying to kill a familiar, or play focused with the fast Remilia taking on all 4 familiars (compared to Yuyuko, or even Alice taking on 3).
As I said, Sakuya being unable to kill familiars in Reisen's 2nd spell isn't a big deal. It was just an observation because Youmu can, even though it hardly makes a difference.
Even if Kaguya's 3rd spell is easy, the fact is Youmu and Marisa can kill the familiars quickly and make the spell even easier whereas Sakuya can't. Though I'll still admit, it is an easy spell, so I won't push that one.
And to be honest, their inability to kill familiars isn't even my biggest problem with the Scarlet team lol. It's just one more thing, I guess you could say the straw that broke the camel's back.
I can't do a replay right this second, but if you really want me to I'll do one tomorrow.
Like I said, I didn't respond because it wasn't the place for discussion. I only wound up responding because I didn't want you to keep reposting it. Next time just make a thread like this instead of getting passive aggressive. That sort of "give your rating" thread usually isn't the place for discussing those ratings, for some reason.