Ive never found it easy to fit cards like Oversold Cemetery into my lists, and have often found myself wanting some more proactive repeatable self mill that doesnt cost an arm and a leg
(If a permanent with a stun counter would become untapped, remove one from it instead.) Whenever you draw a card during an opponent's turn, create a 1/1 blue Tentacle creature token
Reprinted enemy fetch lands like Misty Rainforest and the cycle of Ikoria Ultimatums add long-term value while showing up naturally in boosters
Unexpected Windfall Red gains ramp in AFR via Unexpected Windfall, a four-drop Instant
Boromir is also cheap enough that if you need to sac it, you can easily recast it soon
While there are other cards like Lingering Souls that create similar tokens but also provide additional value by being flashbackable, Shadow Summoning can still see play in the right context, especially in formats where instant-speed token generation is less critical