How many talented individuals are you missing out on because of your rigid ideas about what a passionate and effective employee looks like? There is no reason that a 3 day a week role can’t have a huge impact on your organisation, or someone who only wants to work 30 hours a week due to taking care of a elderly parent or children etc. In fact the research shows that people that work part time and flexibly are MORE productive, not less. Stop work shaming people because they want to do work they care about but do it in a different paradigm. Perhaps two 25 hour a week employees is slightly more expensive than one who does 50. But research shows you will get so much more productivity out of the two part time workers.
I know one non profit that employs two people full-time to cover one position that does require weekend work every weekend, as well as availability at nights. The two job share and are paid for full-time work, that share an inbox and work plan, and get to compleletly switch off when they are not at work.
If, as employer, you want to get the best talent, then these are the creative solutions you need to be open to. There is more than one way to meet your business needs.
Stop work shaming people who want work they care about AND want to negotiate conditions that work for them and meet the business needs at the same time.