The extension does these checks. It checks that the game folder is "tf" and that the CTFPlayer server class and the DT_TFPlayerShared data table both exist. You're getting the first error message, so the game folder check is failing.
Even if you do manage to get it loaded, you'd still have to make sure all the gamedata is correct for your mod, which is unlikely to be the case.
If you can find someone that is interested in the project, I'd recommend forking the SourceMod codebase (just for the extension), patching the folder checks in the extension and any plugins that do their own, and maintaining your own gamedata files.
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