How do I balance a designer's craft with deadlines and constraints?

You respect the craft, and you feel the pressure of the deadline, and those two pull in different directions. That tension is not a sign you are doing it wrong. It is the actual job. Good work lives in the space between what is beautiful and what is possible, and someone has to hold both. That someone is you. The mistake is treating constraints as the enemy of craft. They are not. A real deadline and a real budget are part of the problem the designer is solving, just like the pixels and the type. When you bring the limits early and honestly, a good designer does their best thinking inside them. When you hide the limits and spring them late, you get resentment and rushed work. Next time you brief a designer, name the constraint out loud at the start, not the end. Say what is fixed and what is open. Then trust them to work within it. You are not clipping their wings. You are giving them the shape of the real problem, which is the only kind worth solving well.