It's still useful. It's practical. (Layer underwear IS better than mesh underwear.) And, more importantly, it's LEGAL. Also because Linda was one of the few creators to actually put their stuff under a license.
Yes, many OpenSim users want their OpenSim avatars to look like state-of-the-art, top-of-the-line Second Life avatars. Legacy body, LeLutka head, EvoX skin, Doux hair, the whole shebang. If they knew about ARC and how to display it, they'd probably think it's the measurement for good avatar looks.
Some OpenSim users would even like to enforce a minimum content quality standard, particularly for avatars, that absolutely requires avatars to be completely decked out only in ripped SL content and in all mesh except for skin, make-up and tattoos. They'd probably also enforce certain avatar styles: Male avatars would have to be either badasses or sexy beach boys, female avatars would have to be cartoonish Kim Kardashian caricatures clad in the raciest, skimpiest, sluttiest outfits possible.
But some of us refuse to use illegally ripped SL content on our avatars. We prefer a free, open-source, made in OpenSim for OpenSim, LEGAL Ruth2 v4 to a stolen L$5,000 Legacy body with a stolen L$5,000 LeLutka head. In fact, some of us forgo mesh altogether and stick with the system body, layer clothes, unrigged prim attachments and skins from the 2000s to get around having to use stolen content. And because they prefer lightweight non-mesh to unoptimised, single-LOD mesh that inflates your ARC to over 600,000.
@JamieWright is currently working on a sim named "Old School".
https://opensimworld.com/hop/95214 It's a freebie sim that specialises in older content that's at least expected to be legal. Linda Kellie including Clutterfly, Nebadon Izumi/Oni Kenkon Creations, Ina Centaur/Open Avatars, stuff from FleepGrid etc. There's still a target audience for this kind of stuff.
I know that not few OpenSim users would want her to delete her sim, her non-mesh avatar and herself from OpenSim for good and make way for the next R. Lion/Starchild/Sciattisi/TdV, another freebie sim that offers tons of freshly ripped premium SL content for free. The kind that'd constantly be in the OSW top 10 if it had an OSW listing.
But she won't do that.