The deck that makes the most use of Solitude is probably 4c Elementals where it can be tutored up and then Ephemerated for some crazy value , but it is also vital for Azorius Control where it represents one of the few threats the deck can present
This is a distinct metagame, with its own rules and structures
Sometimes you want to cast it during your opponents turn so that you can untap and play the new things you drew, but sometimes that additional life is great
Ah well, I think that's only a limitation that matters for a short period of time, as most people aren't going to care three months after release if your flashback deck had Grizzly Fate at the same time as your populate deck had token making engines
Unfortunately, the immediate discard requirement and potential to miss an OHKO make it too situational
Much like Oko, Thief of Crowns before it, Uro showed how tricky it is to deal with three-mana cards which can offer both battlefield presence and turn-on-turn resource advantage