A developer is a scalpel. A founder is a swiss army knife.
It's really as simple as that. As a dev, you're focusing on using technology to solve problems, one feature at a time. You — hopefully — can get into a flow state, create a mental map of the system you're working in, and then operate on it with surgical precision, solving a clearly defined problem. You might even have requirements and a well-defined solution state to reach.
All of this stops when you're a founder. Your challenges are nebulous and often evade any chance of being defined. There are no well-defined states to reach, just running experiments that may or may not work out. It's often very much the opposite of coding: you have no compiler or interpreter to tell you if things will work or not: reality is that for you, and reality has horribly long compile times.
The good thing about becoming a founder is that the elasticity required for it will broaden your mind. If you are responsible for the whole business, you start seeing the technical implementation as one of MANY things that need to be done. You reprioritize things. That often leads to more pragmatic choices: instead of building the business on the newest Vercel-based serverless stack, you might just go with a quick prototype built with Ruby on Rails because that is the language you know. Instead of reading through the documentation of the latest k8s offering, you run your little web app on free Heroku dynos for the time being.
Being a founder teaches you to juggle — which is the opposite of a flow state.
I found that incredibly hard as the person building tech in my own startup. I had to be there for customers AND build features for them. It was the worst when there was an emergency: I had to fix our deployment while telling hundreds of customers through chat that I was working on it.
But I got through it, and I see other developer founders get through it every day.
It might sound scary, but it will turn you into a much more pragmatic developer. And, if you choose to build a business, you will use your technical skills — when you take the time for that — to build something that is valuable and owned by yourself, not some employer somewhere. That is incredibly motivating.