You critique your homilist all the time. Talking with other parishioners, around the family table, at work, and in your mind over and over, you've formed a lot of opinions about what your preacher says. Most preachers get very little feedback from the assembly. But preachers have ways of finding out what people think.
Preachers have a general idea how attentive the listeners are.
But most preachers don't get systematic feedback. And homilists rarely get to hear each other. You may try out several different preachers in the course of a year, but homilists don't. They work on Sundays. If you've got something to say to your homilist, you'd do the whole parish a favor by speaking up.