Guantanamo is indeed a horrible authoritarian injustice but it is not the same. Gitmo is operated by the US government and people detained there can still have access to legal representation to challenge their detainment.

What is happening here is the US government sending people to a gulag operated by a foreign nation and then insisting that that's the end of it. There can be no meaningful challenge of your unlawful detainment. With CECOT your only opportunity to vindicate your rights is at the literal moment that you are grabbed off the street.