The player has slow feet. He is slow. It is a fact. Defensively he might have gotten better. When you were already a terrible defensive player, please define better?
Well even though you speak your opinions as if they are are fact, Kelly being slow is as debatable as Kelly being a poor defensive player.
I wouldn't describe Kelly as quick or explosive by any stretch of the imagination but he's also by no means a slow lumbering 7 footer either. Kelly may not be a full court rim runner, but in the half court he's more than capable of pump faking, blowing past his man, and taking 3-4 long strides to bound his way to the basket before the defense has time to collapse.
If a fast short player gets to the basket in the same amount of time that it takes Kelly to long leg lurch his way to the rack who care's how "fast" his feet are?
Kelly is a terrible defensive player? Why, because he looks lost when he get's caught giving up awkward and 1's where he can be seen plummeting to the ground as his man beats his chest and flexes? At least he was in position to defend the shot in the first place.
What about all the shots he's stops before their taken by keeping strong defensive positioning? Kelly's a space eater with a knack for knowing where to be to disrupt the flow of the other team's offense. I see a pretty [darn] good defensive player and the stats back it up.
Kelly is currently ranked a respectable 23'rd of 69 eligible centers in ESPN's Defensive RPM stat (
https://www.espn.com/nba/statistics/rpm/_/sort/DRPM/position/9 ) ahead of guys like Drummond, Embiid, Biyombo, Al Horford, Hassan Whiteside, and Marc Gasol. While that's not to say that those are bad defensive players, it's just as ridiculous to conclude that KO is a bad defender when looking at who he's measured up against.
What Kelly Olynyk does on the court works and IMO we're fortunate to have him.