It’s easy to come to that conclusion based on the facts and that reasoning. Couldn’t we say the same about him if he was on the Brazil national team? Or is the author saying he’d still be picked regardless in Brazil because a lack of other options.
Everyone knew he would be a difficult fit for the Spanish side and he hasn’t helped himself with his lack of impact. The behavior thing could be approached differently by a coach of a different nation but I don’t see Dunga straying to far from Del Bosque’s reasoning either. When fit, focused and on form Costa still is one of the best forwards around. Start scoring goals again and he’ll be picked and, eventually, he should adapt to Spain or vice-versa. If he adds some better discipline to that then there’s no reason he won’t be a regular.
He’s been picked because of two specific things, either injuries or behaviour, not because he’s shit. I’m pretty sure he still got picked whenever everything was fine as Del Bosque tried to fit him in. It’s not a waste until that stops happening altogether.