Are feet a sex thing? "No they're for walking," you might say, but to some people, they definitely are a sex thing.
The world isn't so black and white to where you could definitively say anything is or isn't a sex thing. No matter what you're thinking of. Yes, even that.
A better question to ask is, "Is furry predominantly/exclusively a sex thing?"
For most furries, the answer is "No". The furry fandom has a lot more to offer than that. We're a friendly and accepting community that celebrates authentic self-expression and innocent fun.
For some people, sex might be part of their interest in the furry fandom, and that's okay. So long as they're not hurting anyone (human or otherwise), and they're respecting others' boundaries (i.e. by keeping their activities behind closed doors), and everyone involved is having a good time, why does any of that matter to you?
But even with those people in mind, there aren't many furries for whom it's as simple as "a sex thing" and nothing else.