Conley has had a couple big injuries that ended his season, but nothing out of the norm in a long career.

Drafted in 2007
First major injury wasn't until 2015-2016 he missed 20ish games and the playoffs with a foot injury

2016-2017 had had a fractured vertebrae and was supposed to be out 6-8 weeks, but was able to return after only 9 games.

2017-2018 was the big one with an Achilles injury that had him miss basically the entire season.

So in 14 years the guy has had 3 major injuries and was basically healthy all the time until 2015, 8 years into his career.
If you want to argue he's struggled with injury over the last 5 years or so, that's fine, but prior to that he was very solid.

In the 13 seasons before this, he'd only once (aforementioned Achilles injury) played fewer games than Mitchell did this season, in his 4th year.