I would go one step further: everything is okay with your side project.

You don't want to open source it? Don't. You want to open source it but not build a community? Don't build a community. You don't even have to answer to requests.

You don't even have to disable the PR on your forge.

You don't even have to explain clearly in the README how you envision it and show any kind of commitment.

You do you, open sourcing is already nice.

The reverse being that as a user, if you use an open source project written by someone you don't pay, don't behave as if you were a customer.