Most announcements are of the nature "The seat-belt sign is now off to allow you to move about the cabin, however we recommend .....etc."
In which case no, it is not a clear and obvious message that we do not need to keep our seat belts fastened.

Not on all the time?
Not included in the scan?

The flip side of this is many flights where the seatbelt sign is left on for most of the flight, and not just on 1.5 hour hops one city over.
This leads to the fasten seatbelt sign being treated like a 'serving suggestion' with people feeling free to use the restrooms etc with no intervention by the flight attendants.

Seems that a better idea would be a "always fasten seatbelts" policy with the sign reserved and enforced as stay in your seats.

There is an interesting difference in safety policy between air and road traffic here. Where I live, traveling any larger distance by a bus that is not just local and uses a highway, the official policy is to punish a passenger who does not engage the seatbelt with a fine of just around €100. I never saw it enforced, and i doubt that it is widely known. And yet it is the actual rule. But imagine how unthinkable this would be in a passenger aircraft, regardless of how much. and possibly even more, sense it would make. The rules on wearing a seatbelt in an ordinary car are of course widely observed and enforced btw, with an important difference being that by disobedience you would harm yourself in an incident, rarely others.

We are too politically correct in trying to suppress the risks of injury during an unexpected event. Passengers should be told: "You are riding in a plane. It could unexpectedly and suddenly pull you downward with a force exceeding your body weight, or, in the event of an emergency landing, decelerate with a force exceeding 20 times your body weight - we'd like you to wear your seatbelt to hold you in." for your sake, and the safety of people around you.

Two years ago, I ripped a seatbelt right out of a plane, I have experience with being an occupant in a landing gone wrong.

Seems some airlines are more proactive in this regard than others. I fly Lufthansa long-haul on a regular basis and since about a year (two?) ago, part of the safety announcements is something along the lines 'you must keep your seatbelt fastened whenever you are in your seat'. Probably not the exact wording, but it's certainly worded in a pretty strong, unambiguous way.