What FPV Part Categories Are Lacking Most for Builders?

Question about the builder and parts, generally but maybe mostly to devs/reviewers of parts:

What part categories are lacking the most - is it receivers/FCs/ESCs/sensors/something else?

(Mainly looking for where you would like me and others to focus most on trying to add parts as opposed to what I've been doing so far: just grab something I want to work on randomly.)