"What becomes less fun is the after-building part of running the business."
So many of us want to turn our hobbies into side-hustles, or even full companies. But once the "new" feeling wears off, or we finish building the product, it's just business. It's ALL business.
When your hobby becomes a job, a problem, a customer support problem day in and day out, the fun is gone.
I had games in the app stores. I started an escape room business. I tried to make what I love my job, and that all turned out to be "not fun" anymore.
So, now I'm trying to focus on game making, escape room building, etc, as a side project that I can share with friends and others for free and then just shut it down if it's not fun. I'll keep developing websites and being bored when I need to make money.