I'd agree with the parent...there are jobs where passion is key, like a tech evangelist for instance, or a product leader, a salesman, or a founder. But for an engineer, while of course creativity and trying to get better at the trade are important, so are not getting burned out, going through periods of shitty tasks keeping a professional attitude, make pragmatic choices when needed, without getting blinded by coolness or just curiosity.

These skills can come with experience, but can also be personal traits. An employee that doesn't code the week-end but focuses on his job while on site and takes pride in being professional and reliable is a solid asset for any company. In the long term he might be a corner stone of your team, balancing the ones that are half dead because they didn't sleep at night to work on the projects they really invest themselves into.