Our countertops are off-white ceramic tile with black grout. The countertops are all in excellent condition, except for the one on the peninsula where the sink sits. That countertop has several cracked tiles. Some of the cracks are hairline, others are a bit larger than that. None of them are "loose." I think some of the cracks have been caused by the house "settling" in recent years.
If we can fix the cracked tiles, we would consider NOT replacing our countertops, because in general they look pretty nice.
I have a box of tiles from the kitchen countertop with in various shapes. Could a tile person "change out" the cracked tiles with new ones? Is there a way to "hide" hairline cracks?