Hello @gizumon,
Thanks for posting this question on the Apple Developer Forums!
Since the data you are looking for is "public" data, it is not necessary to purchase an Apple Developer Account to attain this information. However, I can confirm that as of today, you cannot use the App Store Connect API to collect App Review information about an application that you do not own. The information provided by the API is much more inclusive than that made available publicly.
With that being said, you can still get the data you are looking for by using the RSS feeds that Apple makes available. An example of one is below returning JSON, but XML is supported as well.
https://itunes.apple.com/[Territory]/rss/customerreviews/id=[AppleAppID]/sortby=mostrecent/json
Depending on how complex of a solution you are looking for, you will need to build a fully dynamic solution that supports territory localization along with pagination while not making so many requests that Apple services start to rate limit you. The availability of the service is not clearly documented in any one location and by looking online for the above URL scheme you will find many posters sharing their experience interacting with the endpoint.
Hopefully this helps and happy coding!