Mana and card draw are the most important resources in Magic, so getting both from one trigger plus whatever rewards you get for sacrificing your creatures is a massive advantage
It's annoying and pervasive, but I don't think it rises to the power of the Top Ten, because, well, Slivers are fun, right
The original art book in 1998 sold terrible
Enchantment - Saga Sheoldred, Whispering One Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.) At the beginning of your upkeep, return target creature card from your graveyard to the battlefield
There are a few staples that any Elf deck will love like: Elvish Archdruid Elvish Warmaster Overwhelming Stampede There are several high-power spells in the deck too, like Heroic Intervention and Asceticism to keep your creatures safe, and Genesis Wave to turn your mana into even more creatures
There's absolutely a case to be made for this being the best of the Strixhaven decks, but right now it's a comfortable number two