This is something I’ve not seen much in KDE over the years, but these sorts of call-to-action posts seem to work.
Contributors from all areas could make more posts about crucial or beginner-friendly issues that they feel should get more attention and get them to Planet. This would have the additional benefit of letting others know what projects are struggling with.
I see two ways of going about it:
Help needed with X, Y and Z
Want to make your first contribution to X? Here’s a list of tasks to get started