Here are the stats for shortstop defense in 2018. Clearly, Anderson has shot up from the bottom of the list, where he was around the end of April. There are improvements in UZR, defensive value, and DRS, where he has crept out of the negative range. He has been improving defensively throughout the season while Manny Machado, who many can't wait to kick Tim out of SS, has been abysmal out there.
I'd love for us to sign Machado but I think he's a disaster at SS and putting him there on a (supposedly) contending team would be very unwise. Anderson is the better SS defender by far. Manny simply doesn't have the range to play SS.