Is it truly possible to create an online community?
Yes, but no.
The right way to think about it is that you're creating the best place for a community to come together.
There are many reasons why you don't want to approach the task as "creating a community."
You really want your members to feel that they've created the community. You are only the agent; you are the jelly-like stuff in the petri dish. Members who feel an ownership stake in a community are members for life.
For any online community to thrive, it needs to have a defined point of connection. This is usually a passion, a quirk, a bond that makes the members feel kinship with one another. It might be a love of Steampunk. It might be that they are Masters students in Philosophy. It might be the fact that their parents were in the Army when they were young. You didn't make those things happen, they just are.
When a community speaks with a common voice, common lingo, common traditions, it's a beautiful thing. Generally, this type of deep relationship springs from true human connections. That is hard to fake, and very hard for a brand to gin up in the marketing department.
So what's a brand or business to do?
Find the community that already exists in your niche, and give them a playroom. Let them name it, play with it, and run it if possible. Then maybe they'll do you the honor of inviting you in.
Have you found your community yet?