If it's cleaning the metal parts, then it's actually removing the oil or grease that would lubricate the mechanism. WD-40 displaces and repels water, which can make it a good choice for coating metal you need to store, and it strips oils, which makes it useful for removing old, dirty, lubricants, but it doesn't really take their place. It can be good for loosening surfaces than have bound together, but that's its cleaning function, rather than lubrication.

You'd be better off getting some proper lubricating grease for your garage door, but don't use too much, or it'll tend to trap dirt, and you'll need that WD-40 to clean it off before reapplying it!

Depending on what you are unblocking, grease or simple oil can be a longer term solution