I want to separate two things here, because they deserve very different verdicts. The learning path is good. The certification is optional at best. The free material on Microsoft Learn that prepares you for GH-900 is a clear, sensibly sequenced introduction to Git and GitHub that covers more ground than the tutorials most people cobble together, and importantly it includes the areas self taught users tend to have gaps in.
Branch protection, repository permissions, organisation administration, the security features, GitHub Projects, the licensing and privacy settings, all the unglamorous platform knowledge that you only pick up by accident when something breaks. Working through that is time well spent whether or not you ever book the exam, and I would recommend it to anyone who learned Git by memorising four commands and has been getting away with it ever since. I also think GitHub was right to aim this at non developers as well as developers. Product managers, technical writers, designers and analysts all live in GitHub now, often with nobody ever having explained the model to them, and a structured path that assumes no prior knowledge fills a real gap.
The exam itself is competently run, with a free practice assessment and a sandbox so you can see the question format before paying, and a hundred minutes is comfortable for the scope. So why only a middling rating. Because the credential solves a problem that GitHub users, uniquely, do not have. GitHub is the one platform where your competence is already public and verifiable.
A hiring manager can look at your profile, see your commits, read your pull request descriptions, and judge how you actually work in about ninety seconds, and that evidence is far more persuasive than a beginner badge. For almost every other tool a certification exists because there is no other way to show what you know, but here there is a better way and it is free. That makes the exam fee hard to justify for the typical self funding developer, especially at beginner level where credentials carry the least weight anyway. The content also overlaps almost entirely with the first few weeks of any reasonable bootcamp or full stack course, so a lot of people would be paying to certify something they already covered.
Where I do think it makes sense is narrower but real. If you are on an apprenticeship or a graduate scheme where a formal credential is required, if you are a career changer with no portfolio yet and you want something concrete on an otherwise empty CV, if you are non technical and need to prove platform literacy to a sceptical team, or if your employer has a training budget that expires, then go ahead, it is a reasonable thing to spend it on. My advice for everyone else is simple and slightly contrarian for a review site to give. Take the free path, absorb the administration and security material properly because that is the bit you are actually missing, then skip the exam and put the ninety nine dollars toward something that teaches you a skill you cannot already demonstrate with a link to your profile.