Compared to what they have now at SS? At least Simmons was known to be an elite defender. Even with the bad hitting Simmons was still a 2-3 win player.
Simmons' best seasons offensively came when he pulled the most fly balls. He is a glowing example of why guys want to pull more fly balls. If the Braves had an analytics department larger than 1 guy and an intern they would have had him make the same changes he made 2017.
As I said, I can't fault the Braves too much for trading a guy who provided most of his value on defense before his defense declined. What I fault them for is wasting other valuable assets by keeping them. Trading Simmons and holding onto Teheran was an inexcusable set of moves for a team to make.