I really like the aesthetic of the local communities for general topic categories; great iconography!
For the lang communities, or communities for projects with widely recognizable or official logos, I'm not so sure about unifying those as well, as it could hamper the visual brand recognition and association of the community with its target focus. For example, with so many communities, it's kind of convenient to be able to quickly glance the list and pick out recognizable interests without even reading the multiple pages of search results or labeled lists.
That said, perhaps there is merit in going fully unified, as then remote subscribers could easily identify communities hosted from the programing.dev instance, a pattern that other instances like beehaw.org or lemmy.world have already set a UX precedent for.
However, beehaw does benefit from having a recognizable shape (a hexagon), along with a high contrast color pallet (black on yellow), making it easier to recognise silhouetted logos, given the high contrast, even at smaller resolutions no bigger than the subtitle font size in Lemmy's post feed. Admittedly, some of the black on purple gradients here look a little dark to read at font height scale.