I use this velcro to stick items under the desk, but even “industrial strength” that has its limits.
As you found with your sticky bits, the adhesive is probably where it will eventually fail. Velcro is weakest on the underside of the desk because the weight works entirely against you, both for the adhesive and the hook & loop. It’s stronger when mounted vertically. It’s pretty good for hanging 2.5" portable drives, but not 3.5" desktop drives. Those are just too heavy.
For heavier things, I’m not averse to using screws under the desk. Whether to add capacity to the velcro (add a washer to the screw and cinch it down tight) or on their own. Nobody is going to see them, so why not?
The velcro didn’t work for my thunderbolt dock because of the weight of the cables, so I 3d-printed a tray that fits the dock and screwed it under the desk. With that, all the cable drag of raising and lowering my standing desk has gone away.