(This might be an obvious hint, but since I only figured it out a couple of years ago, I thought I’d share it in case anyone else hasn’t had this particular lightbulb come on yet.)
When Velcro fasteners, such as those on kids’ shoes, become un-sticky, you can often make the Velcro as good as new by cleaning the lint out of the hook side of the Velcro. Use a tiny crochet hook, a large needle, or even your fingernails to get under the lint and fibers and lift them off the hooks. I usually can’t get every last bit, but getting most of it off can make an amazing difference. If you have a pair of shoes that’s still good except for the Velcro, this can be a thrifty fix.