Finishing a product is a mental model that doesn't necessarily relate to reality in any way. Design of Volkswagen Golf was "finished" in 1974. Wolkswagen Golf built in 2014 has very few interchangeable parts with the original.
Some people need that feeling of finishing a project. My dad lives for that feeling. Personally I don't get that high, no idea why.
Publishing/shipping a product is lot more tangible. Here completely different set of feelings and motivations are at play. Many people hate publishing, because it shows their mistakes to an audience. I hate publishing, usually only shame comes out of it.
The "ship early, ship often" mantra is for people like me who have loads of projects in the making. Some people really don't need it.
So publish unfinished product, then do something interesting?
I think I will do exactly what you suggest, and pick something that's more fun to work on next, rather than what I think I "ought" to.
For now, I'd start a project you wished you had time for before. One you've been longing for. If you can't decide, simply choose one, any one will work, but I'd go for something you think will be easy to medium in work and scope.
While you do that, start thinking about another project you'd like to work on. This helps me the most completely avoid this sort of situation, especially with artwork. I generally have different projects in different stages of completion, and I find my finished work is better if I have variety of projects. The bits that I dislike are interrupted by works in the 'enjoyment' zone, and I can work across projects if I'm in a zone for a certain skillset as well.
I try the same sort of thing with life goals as well, but I've occasionally those get dumped and changed.
I'm going to try to adopt your outlook, and look upon a stable of upcoming projects as an encouragement to tie a bow in what I'm working on at a suitable point, AND an opportunity to switch when things get boring. Thanks for that.
Anyway, I find it silly to continue with xsd2proto if the time and effort don't actually seem worth the opportunity cost anymore.