It’s hard to say if AppleCare on the watch is worth it or not. A lot depends on how hard you are on watches.
That Bering said, if this is your first watch & you’re unsure, it’s probably better to get it and not need it, than to regret not getting it.
I bought it for my first watch (A series 2), but did not pick it up on either of my other two watches (series 3 and Series 5) and all have been fine. But since I wasn’t sure how it would handle my daily activity levels, I’m glad that I bought it, at least the first time around