In his peak defensive season (2016) by UZR, DRS and Statcast, his jump was +1.0 feet above average which is about ~0.3-0.5 feet from being in that elite group it seems. He's consistently rated well by route, but his reaction has usually been around average with his burst declining year by year, likely as a result of aging and the wear on his body from all those diving plays. The interesting thing is that although his sprint speed has never been in the upper echelon, certainly not for CF, he was still making a lot of those difficult plays. So something about his closing speed, or the ability to maintain his top velocity combined with taking good routes and his lack of care for his body on diving opportunities is what made him so good despite his jumps being nothing special.
With that said, Statcast has never been a big fan of Pillar since 2016, seemingly placing him as more of an average CF, whereas DRS loved him in 2017 with UZR a fan but more reserved, then a decline in 2018, and a much steeper decline in a small sample in 2019.