Bronze, or honestly even sub-bronze unranked.
The game has gotten easier.
You don't have to time dragons, know jungle spawn times, and flash was about twice as strong then.
Dying rapidly reduced how much gold you were worth, so blindly killing your opponent over and over again didn't confer as much benefit then as it does now and shutdowns went up to 1000 gold. So getting too far ahead could be a folly if they had a chance at coming back.
Silver back then was the point where like...you actually knew what was happening in the game and were a bit above the average (I wanna say it was like 1200-1400 Elo?) Bronze was 1000-1200 I think, and 1200 is true average.
So anyway, yeah, now that silver 3-4 is the true average range, and there was a hell of a lot more to think about rather than just eliminating your opponent repeatedly, they'd probably be lower tier, because they'd still be terrible at farming, and that meant more back then than it does now.