Games like Nutsimilian
Games like Nutsimilian include People Playground, Factorio, RimWorld, Terraria, and Space Engineers. We matched them by the tags players give Nutsimilian on Steam (Simulation, Sandbox, Moddable, 2D, and Pixel Graphics): closest matches first, and among equally close ones the better-known games.

People Playground
Shared: Sandbox · Moddable · 2D

Factorio
Shared: Sandbox · Automation · Resource Management

RimWorld
Shared: Sandbox · Simulation · Moddable

Terraria
Shared: Sandbox · 2D · Pixel Graphics

Space Engineers
Shared: Sandbox · Simulation · Survival

Oxygen Not Included
Shared: Sandbox · 2D · Simulation

Garry's Mod
Shared: Sandbox · Moddable · Simulation

Kerbal Space Program
Shared: Simulation · Sandbox · Moddable

Game Dev Tycoon
Shared: Simulation · 2D · Moddable

Cities: Skylines
Shared: Simulation · Sandbox · Moddable

Stardew Valley
Shared: Pixel Graphics · Simulation · Sandbox

The Sims™ 3
Shared: Simulation · Sandbox · Character Customization

Graveyard Keeper
Shared: Simulation · Pixel Graphics · Sandbox

Airport CEO
Shared: Moddable · Simulation · Sandbox

Dyson Sphere Program
Shared: Simulation · Automation · Sandbox

鬼谷八荒 Tale of Immortal
Shared: Simulation · Sandbox · Singleplayer

Prison Architect
Shared: Simulation · Sandbox · 2D

shapez
Shared: Sandbox · Automation · 2D

Forager
Shared: Pixel Graphics · Sandbox · 2D

Starbound
Shared: Sandbox · Pixel Graphics · Survival

Cities: Skylines II
Shared: Simulation · Sandbox · Moddable

Potion Craft: Alchemist Simulator
Shared: Simulation · 2D · Sandbox

Elin
Shared: Character Customization · Pixel Graphics · Sandbox

TheoTown
Shared: Simulation · Sandbox · Pixel Graphics