When you’re starting a company you have to be passionate about the problem you’re solving. That’s a truism of entrepreneurship. You’ve got no customers, no employees, no activity: You better hope that the vision you hold in your heart is one that keeps you excited through all the days (and years?) of little progress.
When you’re joining a company as an employee, by contrast, passion for the problem the company is solving is less important — assuming the company already has some traction, which is a fair assumption given the company has the cash to hire you. Why? Because anything at scale is interesting. You can take the most boring, back office piece of enterprise software and if you tell me, “Millions of people use this every day” or “50 companies are paying millions a year to use this” etc. then I’ll become interested. Heck, if you pitched me on joining a trash pickup business like 1-800 Got Junk and you said they’ve got 200 different locations and are doing tens of millions a year in revenue — I’m potentially interested. Ideally, the business mission also aligns with something you’re personally passionate about, but it’s not necessary.
Bottom Line: When you’re founding a company (or joining a super early stage company), passion for the problem the company is solving is critical. When joining ventures that already have velocity, other factors — like the quality of your co-workers and the culture of work that’s been established — matter more, because anything at scale becomes interesting.