Anyone with access to root cert can decrypt the data
Not directly no, but it could be combined with other attacks to potentially decrypt your data. Maybe.
The root certificates are used for the primary proof that the server you’re talking to is the server it claims to be. It’s not the only protection so just this alone wouldn’t generally be enough to decrypt anything. Also if your traffic does go to the correct server… then having the root certificate doesn’t allow them to decrypt it.
It’s a complex system and difficult to explain all of it, you really just need to learn how every step of the process works and also how each one can be compromised, to fully understand any of this.