Helyme was attacked by the Reapers 300,000 years ago, long before there was a Prothean Empire. The destruction of that planet's ecosystem occurred then.
The Reapers were aware of Earth 50,000 years ago, but they chose to spare this planet for the next wave of destruction.
A major problem with the ending is that it contradicts, and even ignores, the canonical lore. One possibility I see mention is that the stranded races would be able to navigate to their homeworlds. Here is what the Codex says about navigation in the galaxy:
Even mass-effect-FTL drive is slow relative to the volume of the galaxy. Empty space and systems without suitable drive discharge sites are barriers to exploration. Only the mass relays allow ships to jump hundreds of light-years in an instant, the key to expanding across an otherwise impassable galaxy. (Citadel Space)
The Codex, also, states that only 1% of the stars in the galaxy have been explored. The Migrant Fleet used the Mass Relays, like every other species, to get to their destinations.
The Reapers were aware of Earth 50,000 years ago, but they chose to spare this planet for the next wave of destruction.
A major problem with the ending is that it contradicts, and even ignores, the canonical lore. One possibility I see mention is that the stranded races would be able to navigate to their homeworlds. Here is what the Codex says about navigation in the galaxy:
Even mass-effect-FTL drive is slow relative to the volume of the galaxy. Empty space and systems without suitable drive discharge sites are barriers to exploration. Only the mass relays allow ships to jump hundreds of light-years in an instant, the key to expanding across an otherwise impassable galaxy. (Citadel Space)
The Codex, also, states that only 1% of the stars in the galaxy have been explored. The Migrant Fleet used the Mass Relays, like every other species, to get to their destinations.