There have been times when community stuff broke through. 6th edition dark elves had a pretty dire army book, and a homebrew errata document circulated via druchii.net became popular enough to see adoption via some independent events before eventually being canonized outright in white dwarf. Also there was a homebrew chaos dwarf army book during 7th edition that saw wide adoption by independent events before GW eventually put out their own replacement via the forgeworld Tamurkhan chaos dwarf rules and model line. There's also the example of early AoS, where GW published an unfinished and nigh unplayable game without points values or army building rules or pick up game friendly scenario packs. That vacuum made room for various community groups to try to fill in the gaps via homebrew, and there were a few competing attempts to do so before GW basically picked a winner to bring in house and canonize via the first General's Handbook.
It's pretty clear that ~a lot~ of Old World players consider the Legacy factions to be a full part of the game, which leaves a major demand for support and updates that the Old World devs thus far have not been allowed to fulfill. That naturally creates an opening for community efforts to step in. Of course, community action invites fragmentation, with different parts of the community seeing different problems and preferring different fixes. In the old Dark Elf and Chaos Dwarf examples above that sort of fragmentation was avoided mostly thanks to warhammer faction communities of the time being largely concentrated among a handful of dedicated forums. Nowadays that's much harder, since the old faction forums are mostly defunct or ghost towns, and modern communities are split between reddits and discords and facebook groups and podcasts and youtube channels and various other social media sites. In the AoS case it's hard to say if a single agreed upon standard would have eventually taken over if GW hadn't picked an official winner themselves, though I do think the community was moving towards consolidation at the time.
The Renegade pdf has managed to break through, in large part because of how prolific and vocal the square based crew is, the size of their existing podcast/youtube audience, the credibility they can claim thanks to their experience running events for other games before Old World and for Old World specifically pretty much since its release, and yeah the fact that have been running some of the larger and more regular Old World events means there are significant competitive events that will use their rules, giving them basically a free pass over the first and biggest hurdle towards wider adoption of any homebrew content.
