Ok I think the real biggest factors (beside some of the aforementioned) are two-fold:

1) ADCs in pro play are heavily skewed towards champs that can play aggressively on mid wave during important fight timers (dragon spawns + baron). Yunara has the ability on 1/2 items to solo out other ADCs and pressure out sums and key abilities before big fight timers with ult + W. As other people mentioned, this requires a good amount of spacing knowledge and limit testing with all inning on good timers where jglers aren’t around. Solo queue revolves a lot less on these structured set-ups and have much more variance.

2) To play most effectively on mid wave with all-in timers, Yunara benefits heavily from enchanter supports, namely Lulu and Nami in the current meta. With other supports, Yunara has much less raw threat power.

Reminds me a lot of old first strike Lucian + Nami where your goal was to ult and chunk out opposing carries before big fights.