Drones are already geofenced, according to what drone hobbyists have been saying

I am pretty sure that's true for DJI drones, but building your own drone, which is achievable by anyone who can do internet research and competently operate a soldering iron and allen wrench, has no such limitations.

There are a hell of a lot of other legal limitations, though:

You must have direct, unassisted vision of the drone at all times. This means long distance flight and all FPV flight (goggles connected to a camera on the drone) are illegal. I've been told you can get around this by having a "spotter" while you're flying FPV, but essentially everyone in the hobby ignores this, which is fine up until a cop decides to make a problem for you.

You must have registered yourself and your drone with the FAA unless it weighs under 250 grams, which is not very realistic. This involves the FAA getting a bunch of information about you.

You must fly with a remote ID module. This is a fairly expensive device which broadcasts the GPS coordinates of the pilot and drone, and the FAA ID number from the previous step, at all times, over bluetooth, so anyone with a phone can receive the signal if they want. This is widely perceived as a mechanism to enable Karens who wrongly think all public drone flight is illegal to find and harass drone pilots, which already happens at a fairly high rate. I honestly don't even know what the point of this is from a safety perspective, besides to fuck with drone operators and hugely reduce their privacy. I doubt planes can pick up the signal in time for it to matter (not that drones accidentally hitting planes is a real problem to begin with), and anyone with actual criminal intent will just turn the feature off. It's like demanding that everyone install an electronic tracking device on their gun- do you think maybe the criminals would turn theirs off before they commit a crime, or simply not install it to begin with? It applies at all times, even if you're flying at the height of one foot over your own property.

There can be additional local laws. The FAA claims sole jurisdiction over the air, so NYC for instance can't actually ban all drone flight, but they can apparently ban taking off or landing, so that's effectively the same thing.

You must obey FAA flight regulations about altitude. Mostly this means you have to fly under 400 feet, but there are areas, like around airports or various government facilities, that drop that altitude to less, sometimes to zero. Under 400 feet and not at airports is the one regulation that actually makes some sense, everything else is just fucking with drone operators because some idiots panicked and want to do something, even if it doesn't make any sense.

Flying a drone for any commercial purposes- which is defined very broadly and includes posting a video from your drone on youtube- requires an additional FAA license which you get from passing a written test and jumping through a fair number of additional hoops.

A lot of drone equipment either outright violates FCC regulations on signal power or requires you to have a ham radio technician license, which involves passing a test which is mostly not remotely applicable to drone operation.

But the short of it is that most recreational drone operators regularly ignore some or all of these laws, which is fine up until a cop decides to make an issue about it and arrests you, then starts looking for laws you may have broken. It fits into a broader pattern of basically making it impossible to live a normal life without violating enough laws that the government can seriously fuck you over at any time they wish.