tl;dr: The DocuTube addon will be removed from the Marketplace at the end of June, 2020. If you're a programmer and you want to take over ownership of the project, let me know.
Three years ago, I wrote a proof of concept Google Docs app that found YouTube links and displayed videos embedded in a sidebar. It was fun to do and showed some powerful uses of Apps Script in a real way.
I'd made some incremental updates here and there and then worked on a major update over the fall and winter of 2019. During that time, Google updated the platform the code runs on which has been a little hit or miss in terms of usability.
I've had a love/hate relationship with the addon. For instance, it won't work for someone who doesn't have edit rights to the doc. So, what was meant to help teachers and students work effectively isn't a good solution becuase of the way addons run.
Second, there have been some very strange errors that I have no control over, mainly within Google's app engine. There are service outages and access errors that I cannot prevent or handle well. This has meant frustration for users and for me.
In the end, it showed that Apps Script on it's own can be a great place to build simple utilities that help add functionality and usability to systems. But the fact of the matter is that I cannot solve many of the main issues with DocuTube and I'm at a point where I can't commit more time to it. Rather than leave a buggy, unmaintained app in the Marketplace, I'll be removing it from the store at the end of June once everyone is out of school.
If you're a programmer or hobbyist and you want to take up maintenance, get in touch because I'd be happy to transfer the codebase over to you and you can republish with all the same assets if you'd like.
If you were a user, thanks. If you wrote a review, thanks. If you've never heard of it, not a big deal.