Their parries don't work the same. They're not meant to work the same. Kasumi's parries come from DOA2U, but received a buff from those states. That's a problem that you want to discuss with Team Ninja.
You are getting parried. Why would you be disadvantaged when you get parried? When you do an advanced parry, you're committing to hoshinpo, the same way Kasumi does she uses her's lol. That's what it sounds like it. That has to be at a MASSIVE negative in order for you to get them guaranteed.
If not, then they'll recover in time to hit you out of the stance. Like in the middle of performing a string. This isn't a problem with the character's parries. It's not a game problem. This is a personal problem, just a lack of knowledge of how they're used.
You have to go & look through every character's toolset (frame data) with Alpha to make sure you get something, not just those 4. You can't just "parry" & then expect to get something out of them every single time. They all work differently against character's strings & tools.
So if you're getting hit by characters after your parries, then you may not in an advantageous situation because the use of the parries varies depending on the type of move that's being parried.
Ayane & Hayate don't have parries, but they have expert holds. Nor do they escape Kasumi's. If Ayane spins away, she gets hit by 66K for free. If she rolls, 3P+KK is free lol.
Also, ALPHA is NOT Kasumi, plain & simple, so Kasumi getting her advantage always from her's because like I said before, she received her parries from DOA2 & 4 to where she also got buffed in the way that they are used. So again, this is something that you would want to take up with Shimbori, Hayashi & Team Ninja.