Games like Unrect
Games like Unrect include Oxygen Not Included, Terraria, Garry's Mod, Space Engineers, and Factorio. We matched them by the tags players give Unrect on Steam (Indie, Casual, 2D, Minimalist, and Singleplayer): closest matches first, and among equally close ones the better-known games.

Oxygen Not Included
Shared: Base Building · Singleplayer · 2D

Terraria
Shared: 2D · Sandbox · Survival

Garry's Mod
Shared: Sandbox · Casual · Building

Space Engineers
Shared: Sandbox · Building · Survival

Factorio
Shared: Base Building · Sandbox · Survival

Scrap Mechanic
Shared: Sandbox · Building · Survival

People Playground
Shared: Sandbox · 2D · Singleplayer

RimWorld
Shared: Base Building · Sandbox · Singleplayer

Forager
Shared: Indie · 2D · Survival

ARK: Survival Ascended
Shared: Survival · Base Building · Open World

Sons Of The Forest
Shared: Survival · Base Building · Open World

Goat Simulator
Shared: Casual · Indie · Sandbox

Project Zomboid
Shared: Survival · Sandbox · Indie

Game Dev Tycoon
Shared: Indie · Casual · Singleplayer

Zup! S
Shared: Casual · Indie · 2D

Palworld
Shared: Indie · Survival · Open World

Raft
Shared: Survival · Base Building · Building

Hydroneer
Shared: Base Building · Sandbox · Casual

Don't Starve
Shared: Indie · Survival · Sandbox

Plants vs. Zombies GOTY Edition
Shared: Casual · Singleplayer · 2D

Medieval Dynasty
Shared: Building · Survival · Base Building

The Infected
Shared: Singleplayer · Base Building · Open World

Keplerth
Shared: Sandbox · Casual · Survival

ARK: Survival Evolved
Shared: Survival · Open World · Building