Games like Mad Merchant
Games like Mad Merchant include Cookie Clicker, Shelldiver, Factorio, Idle Champions of the Forgotten Realms, and The Alters. We matched them by the tags players give Mad Merchant on Steam (Collectathon, Idler, Incremental, Trains, and Management): closest matches first, and among equally close ones the better-known games.

Cookie Clicker
Shared: Idler · Incremental · Collectathon

Shelldiver
Shared: Incremental · Idler · Management

Factorio
Shared: Base Building · Crafting · Resource Management

Idle Champions of the Forgotten Realms
Shared: Idler · Incremental · Management

The Alters
Shared: Management · Base Building · Action-Adventure

Shop Titans
Shared: Idler · Management · Crafting

Kiwi Clicker - Juiced Up
Shared: Incremental · Idler · Collectathon

This War of Mine
Shared: Base Building · Strategy · Crafting

Bills Must Be Paid
Shared: Incremental · Idler · Management

Nodebuster
Shared: Incremental · Idler · Management

Digseum
Shared: Incremental · Idler · Management

Scritchy Scratchy
Shared: Incremental · Idler · Management

Chef Knight
Shared: Incremental · Idler · Management

Schedule I
Shared: Management · Simulation · Crafting

Sixty Four
Shared: Incremental · Management · Idler

(the) Gnorp Apologue
Shared: Idler · Incremental · Management

Hearth and Hamlet
Shared: Incremental · Idler · Management

Dragon Cliff
Shared: Idler · Incremental · Management

Oxygen Not Included
Shared: Base Building · Management · Resource Management

Stranded: Alien Dawn
Shared: Base Building · Crafting · Management

Transport Fever 2
Shared: Management · Trains · Strategy

Kingdoms and Castles
Shared: Management · Resource Management · Base Building

Tower Wizard
Shared: Idler · Incremental · Resource Management

Mr. Prepper
Shared: Management · Base Building · Crafting