@carltongibson perhaps we’re talking about different things? The fragment tag I mentioned as an example is on the order of 20-40 lines of code, 90% of which are DTL tag declaration boilerplate (see fragment in Wagtail tags. That doesn’t strike me as something that would be hard to land (I’d happily make a separate proposal and PR for it if there’s interest).
AND I don’t want to turn the DTL into Jinja — just use Jinja is a legitimate position
Personally I’d recommend considering the aspects of Jinja (or any similar language) that DTL could benefit from regardless of whether Jinja is supported or not. As a dev, Jinja is only an option if you happen to be starting a new project and have enough of a say in the tech stack to go that way. The power of defaults and the inertia of existing software means there’s lots of devs who will benefit from small improvements to the template language in ways that stay compatible with their existing setup.