It’s not nothing but reddit claims about 270 million weekly active users. So it’s ultimately a difference of about 270 million (especially given that some active users here likely still use reddit and aren’t strictly a loss for them)

It’s a good thing though. The fediverse needs to grow a bit to feel less like a ghost town on less popular communities but when you grow too much you become a shitty community filled with bad decisions and poorly thought out compromises