What if your slogan is true?
Slogans never change anything. They don't grow market share or find you a job or win you an election.
Underneath the slogan, perhaps, is a story. And the slogan well told is a symptom of that story, a shadow of what you're truly up to. A slogan might be evidence that you have a story, but it isn’t a story. A story is something you live and connect with and come back again and again and again.
If the story of your work is consistent, if it resonates with your audience and if you can defend it, then you're likely to succeed. And if your slogan reflects your story, good for you.
Apple has had various slogans through the years, but in every successful iteration of the company, the story has been remarkably consistent: Apple’s story is that they are idiosyncratic artisans producing beautiful products for smart people. That's not a slogan, but it's a useful tool for deciding if you're making something or doing something that you ought to be focusing on.
So sure, start with a slogan. But don't bother wasting any time on it if you're merely going for catchy. Aim for true instead.