Denys I think the percentage that appears in Weblate is misleading and over time it will be more (and that is not a bad thing), is something that has spoken more than once with @jslirola, the maintainers are going a bit against the current, I mean Weblate covers not only the core of Flarum, but also all the extensions of the community, and every day more extensions come out... so it's complicated to cover them all, even if flarum core and the most popular extensions are translated, the percentage of them respect the whole ecosystem of the community is obviously smaller, so we must understand that it is a work that will never end.
Personally, I am very happy with the work that has been done with the Flarum Languages initiative, it has given structure and a lot of ease to translation, as well as protecting the translation packages from being abandoned, as was the case before.
As luceos said, if the technical areas of Flarum are improved, its use will increase and consequently more volunteers will be willing to translate.
Add that at least in the Spanish package we accept suggestions, if someone suggests an extension we will consider it for the next update.
