Knowledge of APIs is not a good indicator of ability in my experience (I have many years of hiring people). So, the 'ecosystem' isn't particularly interesting

Knowledge of APIs is not a good indicator of ability in my experience (I have many years of hiring people). So, the 'ecosystem' isn't particularly interesting and neither are the devs that just put endless lists of acronyms on their CVs. It's much more useful to listen to a dev tell you how they solved various problems, dig into their CS knowledge, see what they like working on in their spare time (code or not code related).