As someone that generally likes their day to day work, and dislikes arbitrarily Mandatory Corporate Fundays, I really just wish companies would stop this hack days nonsense. It just means I'm going to be more behind on tasks I'm already behind on.
To do a hackdays successfully, I find good projects have already had a lot of personal upfront investment before the hackdays project. The hackdays project then assembles a team of potential labor that might (or often not) accelerate the idea to a demo. And then, even if there's a snazzy demo, you have to engage in a tremendous push after the hackdays to turn them into successful projects.
I can just as easily spend my time doing this in normal planning channels. And instead of hackdays, maybe we should encourage prototyping and demos to be part of the normal planning process, not some out of band activity likely to screw up schedules and deliver nothing.
Please, companies, stop these mandatory corporate fundays. And just fix your normal planning processes.
So with that in mind, as a leader, I view them as opportunities for sanctioned on-the-job learning. I would hope that you spend the time automating existing processes or learning a new technology that might be useful. At our most recent company hackathon, we focused on a new way to do the old thing. Everyone could build basically whatever they wanted, but they had to use the new tool to do it. Not because we want the output, but because we want everyone to feel comfortable with the new tool. There was zero expectation about turning anything into a production project, although we did have two projects come out of it that are likely to go to prod soon without disrupting the roadmap.
I get where you're coming from, and I agree wholeheartedly with your assessment. If your work is doing hack days, and then getting mad because features aren't shipped, that's pretty shitty of them. Might want to try and find another place with better culture -- easier said than done!