Cloaking of small objects is not uncommon.
You see it widely used. It's often seen as little more than a parlor trick.
The problem comes when trying to cloak an entire ship.
Bending light or imitating light becomes exponentially more difficult the larger the object you are concealing. This is made even more difficult if the source of the cloaking system is to be contained on the vessel it is trying to cloak.
The extreme development difficulty and thus prized nature of this tech is why in the peace treaty with the Romulan Empire, a major stipulation for the federation was for the Federation not to develop or try to acquire cloaking technology.
As of why it is so hard to cloak starships, You have to remember your average Starship is about half a kilometer wide. Even the small Defiant (attack class) and Intrepid class (rapid response class) ships are larger than a typical sports field.
The Enterprise D was incredibly large and designed for diplomatic, transport and other such missions. It was large enough to luxuriously house several thousand people, and massive amounts of cargo. At 43 decks high, with the saucer section being about 20 decks high it's crew and cargo capacity were roughly that of a small city.
Klingon attack ships are by contrast much smaller, with crew space of roughly the size of an attack sub. 126
They are cramped, unsafe and generally not particularly pleasant. Even the larger, more defensive ships are still small.
The Romulan ships while of comparable size to the Enterprise D are designed with substantial modifications to handle the cloaking field and high speed and maneuverability. They still cannot maintain maximum warp with the cloaking field enabled and have much smaller usable ship volume due to these changes.
The USS Defiant was the only federation ship ever to be fitted with a traditional cloaking device.
The Defiant was the smallest full fledged star-ship Star Fleet had made in almost a century. It was only capable housing a maximum of about 50 crewmen with several in each room that was no bigger than a small locker room. This is far less than the 1000+ typical crew/passenger count in the Enterprise D, which could be expanded with the fitting of multipurpose decks and/or cargo bays.
Corrections: Referenced Memory-Alpha Star Trek wiki for more exact information. https://memory-alpha.fandom.com 126