Searching for a new job but not passionate enough about anything...

Instead of asking yourself what you're passionate about, try considering what you're really good at. If your role allows you to do something that you're good at, then maybe it will make going to work less dreadful. You know you can accomplish what you need to accomplish so then at the end of the day you'll feel more fulfilled. 
There was a Ted Talk or some video called "Dont Follow Your Passion." The premise was pretty much just follow good opportunities that arise in your life, and through following opportunities you will discover or develop knowledge and skills in an area, and when you're a beast at what you do, it makes going to work way more enjoyable. 

I found an opportunity to join a firm that invests in new renewable energy developments. At first I didnt know shit about renewables and wasnt necessarily passionate about climate change or anything. Now a year later, I actually enjoy the work I do and the investment process surrounding renewables development is super interesting.