We had common ancestors with sea anemones. We weren't necessary anemones no more than anemones being humans. Parallel evolution led us here and anemones where they are.
> In a billion years you could have literally any lifeform currently on earth evolve into intelligent beings capable of spaceflight.
That depends on how likely is human-level intelligence to arise, so far only one species arrived there and no other. Then you add expectations of being able to build a spaceship capable of escaping Earth's gravity well.
Hoping some future intelligence can do job we can do now is ultimate form of procrastination.
We were nothing more than sea anemones once too. In a billion years you could have literally any lifeform currently on earth evolve into intelligent beings capable of spaceflight. The timeframe is just so unfathomably long thah it's impossible to predict what could happen.