The technical problem is a class name in their code conflicting with a same named definition in their index.d.ts file closely related to that class. If they stopped using classes or changed those names to not be in collision this problem would be cured, which indicates it’s an edge case in their code they could easily fix but choose not to. Knowing that and that they blame the TS compiler for their code problem is cause enough to be judgemental.
Knowing they are aware they could easily fix this issue themselves but are instead dumping TS is cause for hesitation to invest in the project.
