In order for you to play Return to Monkey Island on macOS with minimal graphics settings, your computer must meet the following requirements
Operating System:
MacOS High Sierra and above
Processor (CPU):
AMD FX-4300 (4 * 3800) or equivalent / Intel Core i3-3240 (2 * 3400) or equivalent
Memory (RAM):
8 GB RAM
Graphics Card:
Radeon HD 7750 (1024 VRAM) or equivalent / GeForce GT 640 (2048 VRAM) or equivalent
Storage:
4 GB available space