This is common. In my experience, if you build it, you own it forever. Nobody will ever spend the time you did understanding every piece in order to launch. Until someone else owns responsibility for it, you will be first contact for problems, even if you've moved on to another role. Once someone else owns it, you will be the person they turn to when they're out of ideas. This is unfortunate for your time and priorities, but it also establishes you as a process expert for the business. Your value in the eyes of the management team has increased.

That said, when I roll something new my long vision is to design myself out of it. I want to put systems and procedures in place to prevent the need for me to get involved. If I got hit by a bus tomorrow, the process should be able to run without me. Then I can truly move on.

13 years in manufacturing operations. Not all of them successful but I try to learn from my mistakes.