The company’s model is fundamentally not under their own control, which is a knife that cuts both ways.
That's like saying Facebook's model is not fundamentally under its own control. The same with Twitter, or any other social media.
Calling it a hijacking when it was never under anyone else’s control is not just wrong, it’s actually entirely backwards. Reddit is the one hijacking the subreddits.
Reddit owns the servers which host the subreddits.
Preventing users from accessing your subreddit, as a moderater (who is also not an employee of the company), as a form of protest, is a means of trying to control the website's overall behavior.
So, yes, it is a high jacking attempt. Not an effective one, but one nonetheless.