To activate this card, you must draw it for your normal draw in your Draw Phase while your opponent controls 3 or more monsters and you control no monsters, reveal it, and keep it revealed until the Main Phase 1
What Sidisi does give you is a reliable way to fill your graveyard and access to an awesome three-colour wedge, with some incidental zombie synergy
That's not helpful, but it's also not a showstopper
That trade makes the deck all about finding things you dont mind parting withfrom throwaway tokens to artifacts that replace themselves when they leave
Other high-ranking commanders include Muldrotha, the Gravetide, Edgar Markov, Thalia and The Gitrog Monster, Lathril, Blade of the Elves, and Tivit, Seller of Secrets