Remember
that epic shift Hainsey had against the Predators in the Stanley Cup Final back in 2017?
He generally aims to do the right thing, but cannot physically do it that well anymore and it's unfortunately more and more apparent as the games wear on. Playing on the wrong side makes it even harder; decisions have to be planned out a bit more in advance, positioning and footwork to get there takes just an extra bit of processing.
His purpose is to be an extension of the coaching staff on the ice and on the bench; you don't play as long in this league as he has without doing a lot of the right things consistently. As a player, he is a placeholder for whoever demonstrates they can move up the lineup. As evidenced by their approaches with other Marlie grads these past couple of seasons, the coaching staff does not like their young players getting unsheltered exposure until they've built up a larger foundation of confidence in their performance. Like Martin and Komarov before, someone will be taking Hainsey's spot.