I feel like you're never too late to join a fandom. For instance, it wasn't until late April, that I gave any consideration to the Teen Wolf TV series, the show barely even registered with me. At that time, I was looking for something new to watch after getting caught up on the Shadowhunters TV series. To be honest I'm not even sure how I even wound up with the idea of wanting to watch Teen Wolf but I did and ended up buying the first five seasons on DVD.
Since May, whenever I have the time, I've been watching as many episodes as I can and as of now I'm currently midway through season three. The funny thing is I had no idea what this show was about but I took a chance and wound up really liking it, well at least so far I'm still in season 3 (my opinion could change).
Despite the show nearing it's end (this is the last season), I am totally full on into this fandom. I already pre-ordered part one of season six, ordered Funkos of Stiles Stilinski and Scott McCall, ordered the Teen Wolf novel On Fire by Nancy Holder and bought the digital edition of a three issue comic book miniseries. So, yeah I'm totally on board with this fandom.
I see it all the time where someone will ask "is it too late to join [insert fandom]? The answer is no. I feel like no one should feel reluctant or embarrassed to join a fandom even if it seems like no one else likes it anymore. Fandom never truly dies or fade away because there are always going to be new fans finding it and revitalizing it. Just look at Harry Potter, as I write this new fans are reading the books and watching the movies for the first time.
I don't think it's ever too late to find a fandom nor should you be afraid to talk about any of the new (old) fandoms that interest you. Who cares if you're new to it or just now finding it, all that matters is that you enjoy it.