I think you always need merits, even if it's legendary.
The merits are the recognition that what the person says/does is useful for the readers of this community, whether that person is legendary or not.
Daniel91 is OP of our local thread where members can submit their good undermerited/unmerited posts and that thread has been pretty inactive for quite some time.
I think that in the last six months or so we had maybe 5-6 submissions and that's what he (probably) meant when he said that no one needs/wants merit anymore in our local board anymore as thread used to be way more active 3-4 years ago when me and other members were going through ranks. Its sort of unwritten rule in that topic not to submit your posts once you reach Legendary rank and since majority of us reached that and we don't have many new members, thread became inactive.
Thanks Rikafip, that's exactly what I had in mind when I wrote my previous comment.
I submitted an application in Meta for merit source 5 years ago with the motive to help my local community, because at that time we had many young and active members with low forum ranks.
After that, I started a forum thread in our local board where all members of the local community for the last 5 years could report their quality posts on the forum and get merits.
Unfortunately, this forum thread has become almost inactive for the last year or two, and it seems that my task of helping the local community to progress faster on this forum is completed.
Of course, I still reward every quality post on my local board and in the main part of the forum with merit, but that's a completely different story now.