I've mentioned my love of the series before, so I think I can understand where you're coming from with regards to the large quantity of characters. It can be a little bit overwhelming when new ones show up all the time and you're trying to keep track of it all.
I think what sets it apart for me is that the major characters are all pretty damn memorable in their own ways. There's a fair amount of random background characters that might get named but don't do much, but each character that provides large contributions to the story is unique and sticks out in my mind, especially the Black Bulls. On top of that, I can honestly say that I don't hate a single character in the entire run so far, and that's saying something. Characters that fit archetypes that I'd normally find annoying end up being endearing thanks to the writing. For example, Yuno as the 2kool4skool rival: Yuno doesn't hate or resent Asta, and their rivalry is just how they keep pushing each other to get stronger. You can tell that they really care about each other, even if Yuno keeps egging Asta on.
The elvish possession maybe could have been written a little better to make the personalities more different and distinct, but even if the individual characters are a little samey, those are more of the appetizers to the main course of the end of the arc, which is well worth it. I dunno exactly how far you're into it so I won't get into spoilers, but suffice it to say I enjoyed the hell out of it.
At the end of the day, Black Clover is a pretty standard shonen series, but it plays it straight and earnest and keeps it entertaining throughout (I'm having a hard time thinking of a more earnest shonen protagonist than Asta). I really have to credit Tabata for the writing, managing to deliver a huge cast of characters that I thoroughly enjoy, along with great humor and a standard yet engaging plot. I'm hoping it can continue at that quality in the future.