For Salesforce-like CRM, there's Twenty[0], a good-enough alternative. For Shopify-style e-commerce, Medusa[1] is a headless commerce platform.
The real power comes from using AI to study how these projects implement specific features (payments, inventory, customer dashboards, etc.) and adapt them to your stack. AI excels at finding the "seams" (those connection points where a feature ties into the tech stack) and grasping the full implementation. The trick is knowing precisely where the feature lives in the code (files, functions, modules), because AIs often miss scattered pieces otherwise. That's what I'm building at opensource.builders[2]: turning OSS repos into a modular cookbook with structured "skills" that point to exact details for reliable remixing and porting.
SaaS companies are forever beholden to raising their market cap, even in solved spaces like cart, payment processing, and CRMs. Most businesses run on CRUD apps anyway, and if your core app exposes an API, you can build any customization you need on top of it. People here discounting how valuable it is for a business to have the software that runs their business on a tech stack they understand and something they truly own.
[0] https://github.com/twentyhq/twenty