Many Control players resort to unconventional win conditions such as Laboratory Maniac or the various Jace Planeswalkers and their card drawing and milling mechanics
The thing is, necropotence actually was kind of bad when it was first release, because black vise was something a lot of people played in Standard
Log in RULINGS 2024-06-07 "Flashback [cost]" means "You may cast this card from your graveyard by paying [cost] rather than paying its mana cost" and "If the flashback cost was paid, exile this card instead of putting it anywhere else any time it would leave the stack." 2024-06-07 If a card with flashback is put into your graveyard during your turn, you can cast it if it's legal to do so before any other player can take any actions
Still, plenty of white decks run Farewell despite it being bad on some modes for them, and while Final Act is a bit meme-y in hitting Battles and removing counters, certain control-oriented builds in Grixis and Dimir especially would be happy to play this
Casting it as your first spell with Shiko and Narset, Unified lets you use the treasure to cast a follow up and copy it
All you need to do is pick the one that best suits your needs