Full disclosure I'm a founder of cbk.ai and chatbotkit.com, where we've built reusable agent components. I have never really saw flowise, n8n the now defunct OpenAI agent builder and other similar products as competitors and I wanted to describe why.
I think workflow builders are mostly the wrong mental model for AI. A graph of predefined nodes and edges is useful when you already know the exact sequence of work.... but the point of an AI agent is that it can decide what to do next from the current context.
IMHO reusable building blocks still matter enormously. You should not have to recreate an integration, a capability, or a piece of reliable deterministic logic every time. It is wasteful and you cannot oneshot it. Even with coding agents which we use all the time system to system connectivity is more complex than writing the code. But those should be available to the agent as tools, mechanics, and features that are not wired together as a visual workflow of sorts.
A product can look graph-like at a glance though, while avoiding making a workflow builder. I think this still matters in order to put a mental model around it. But the mechanism should not be graph / workflow like in practice.