I tend to agree with you to a certain extent on that point, because it would definitely make it harder to make an attack like this.
I think this was discussed in the community, and one of the arguments against it was a comparison with how major stores like the App Store or Play Store handle it. The reviews are not bound to paying users only.
So maybe a compromised solution could be some sort of reputation system for (free) users. So, for example you need at least x amount of time on the platform to be able to leave a review, you would at least need to run an actor before you can leave a review. On addition to that reviews would have a badge on them to tell everyone if the users are a paying or free user. Also, all users would have the option to report a review for different sorts of illegal content. This is actually necessary for every platform that provides user generated content under Article 16 DSA of EU Law, so this needs to happen at least.