That's right. You can only see ratings in your feed because they're left by people you follow. You can't otherwise read what other people said about someone else's game. The More Information box on each game page shows its overall star rating, but nothing else.
Viewing post in Ratings and Reviews: where to find
Uhm. Not exactly. It does not matter if you follow an account. That does not give you special access to their activites. You just have them filtered into my-feed and get a notification.
The setting in the account is, what matters.
( ) Make my public activity on itch.io visible to my followers and other users of the site
Reviews appear in the global feed https://itch.io/feed?filter=ratings
The wording of the setting is redundant. The latter category already includes the former. And the explanation below is not exhaustivly, so users with privacy concerns might be worried what else is considered "public activity".