In the Renegade Open which was a big GT took place before the Chapter Approved released, the armies that went 5-1 or better (Eldar highlighted) as far as I know:
Imperium Soup (6-0) by Aleong
Guilliman with Stormravens by Northington
Mass cultists + Death Guard + Magnus by Root
Chaos Soup with cultists and Mortarion by Henly
Foot Imperial Guard with 6 Primaris Psykers, 4 Astropaths, Celestine, 4 Taurox PRime, lots of mortars by Gonyo
Chaos (unknown composition) by BarkleyYnnari
IG with Grey Knights and Celestine by SansoneCraftworld Eldar (Alaitoc)
with no Ynnari by Schuchman
Pampreen's Ynnari did not use Shining Spears. Schuchman's Craftworld Eldar (without Ynnari) DID use a big and expensive unit of Shining Spears. He also had a lot of dark reapers and a lot of Rangers. At least from this view, it seems like Shining Spears are actually more used in regular craftworld eldar detachments than in Ynnari detachments.
Pampreen's list included a Ynnari detachment with:
2x5 Wraithguard with D-Scythes
8 Shadow Specters (this was pre-nerf)
2x5 Swooping Hawks
10 Dark Reapers
And an Alaitoc detachment with:
3 Wave Serpents
Interestingly, since most of the Ynnari Eldar also had the Alaitoc keyword, the Wraithguard and Dark Reapers could embark in the Wave Serpents. Also, Ynnead's Will doesn't require the target transport to be Ynnari, just Aeldari, so Yvraine got by just fine. This allowed the Wave Serpents to benefit from Alaitoc Craftworld trait even if their contents couldn't.
So, no shining spears there in the most successful Ynnari list. What about the other Aeldari list that went 5-1, Schuchman's Craftworld Eldar with no Ynnari?
Farseer and Warlock Skyrunner
2x5 Swooping Hawks
8 Shining Spears (!!!)
5 Howling Banshees (!!!)
9 Shadow Spectres
9 Dark Reapers
2x3 Dark Reapers
My impression is that the Wave Serpent carried Banshees and Spiritseers, but it could also have sheltered 12 Dark Reapers from Alpha Strike instead.
So Pampreen's Ynnari did not use Shining Spears. Schuchman's Craftworld Eldar (without Ynnari) DID use a big and expensive unit of Shining Spears. In fact, he ALSO ran a unit of Howling Banshees!
At least from this view, it seems like Shining Spears are actually highly useful in Craftworld Eldar armies, or at least you can make a winning army containing them--and Banshees! And the successful Ynnari army was one with no Shining Spears: what a twist! With Shadow Spectres being much worse now, i think we'll see a change to armies holding them, maybe creating more room for the close-up shooting Shining spears are good at. Since the Renegade Open GT happened right on the heels of the huge Ynnari nerf, I'm not sure if it applied.
EDIT: as an aside, it looks like Barton's List from Heat 2 GT included 40 (!!!) Dark Reapers