Well the event quests in this game so far haven't been little off-shoot "oh it's Christmas in genshinland, so let's have a fun little side story", they have actually been relevant to the overall lore and plot of the main game. Once you get caught up with the main story quest, it's probably worthwhile to watch the cutscenes only from the Mona/Albedo events, at least if you care about the story at all.
Like
BJK
mentioned above, you also missed a free refine sword that is pretty good for the main character and a few others, but the only area it's really useful in is the snow mountain (which is a way off for you yet). You can easily get by without its damage bonus, though it is handy.
Limited characters have been most of the post-release characters unfortunately, so you missed Venti (best wind character and pretty much broken in multiplayer), Klee (really strong fire mage), Childe (melee/ranged switching water character), Zhongli (kinda shitty geo support, getting buffed), Albedo (good geo support character), and we're currently on Ganyu who's the strongest and easiest to use character yet. Rerolling for her is highly recommended if you don't mind the process, it takes like a half hour at least to reroll properly each time though, so it's not for everyone. I don't know how much the reroll process has changed since launch, but you essentially want to spend the majority of your rolls on the limited banner with Ganyu, she is not available from the standard or beginner banners.
The characters you have are all guaranteed characters that you get for free either through the story or that beginner banner (which you should absolutely roll both times eventually). You will also get copies of Xiangling (fire spear) and Barbara (water healer catalyst) for free eventually by playing the game as well. We also have an event coming up in the next patch to give you any one of the Liyue (the China like area) characters for free, so you should probably have your account rerolled and settled by then, which is at least a week + away.
There's a good chance that this is too much info with weird words and names you don't understand yet, so if you're not interested in rerolling, just play and enjoy the game and pick it up as you go.