As someone who once depended on ASAP artillery fire to keep the enemy from getting through the wire, I can understand those concerns. I want the artillery available. BUT, that kind of fire can come from existing artillery. It might also be noted that, with a minimum of training, 105mm & 155m artillery crews can be assigned to either towed or self-propelled artillery with a minimum of training. I can understand how the Crusader would be considered high maintenance, limited in flexibility, and more suited for a mission better handled from the air.
I don't know about the Crusader's maintenance requirments, but it has some interesting features. It employs MRSI to drop 8 rounds on the same spot at the same moment- like having a couple of batteries coordinate time on target. Needs a specially cooled gun tube as well as a computer. Operates with a small crew and swaps parts with the main battle tank.