The topping on your crumbles and crisps should be sandy, crumbly, and/or crunchy. If you aren't achieving the desired texture, check the ratio of flour:sugar:butter. It's likely that your topping doesn't have enough flour or butter. It's also possible that your crumble is underbaked and the topping doesn't have enough time to crisp up in the oven. Also note that the topping will soften as you store your crumbles and crisps. It's inevitable because of the moisture of the fruit layer tucked below that will soften the crisp topping over time as the topping absorbs moisture.