Yes, crunches can be effective even if you can only lift about 1/8th of an inch. As you progress, your crunch will increase. Crunches are not about a huge lift off the floor, like a sit up is.
There are many other ab exercises to do also. Mix them up to hit your abs in a variety of ways. Again, don't forget to do the opposite exercises also- your lower back. As mentioned, planks are one of the absolute best core exercises to do.
Do or don't do; there is no try (Yoda)