Back when the NES was current, I got one for my birthday. I connected it using the RF thingie to my cheap noname 14" CRT TV bought a couple of years earlier, in the late 1980s or 1990 or so.
The picture was always quite "noisy", meaning it looked like when you were looking at a television broadcast with bad antenna reception.
But now, when I have a different (but identical) NES, also with an original RF thingie, hooked up to my 1989 JVC TV, it's basically impossible to tell it apart from when I use the RCA/composite cable instead. There is certainly no "noise" at all; the artifacts are more like bleeding colours and distortions of a different kind, just like with a composite signal.
What does this mean? The TVs are from the same era, albeit one was clearly much cheaper than the other. I doubt the NES was damaged in any way, nor its RF thing.
What could explain the difference in picture?
Neither now, nor then, was there an actual antenna cable plugged into the TV at the same time, so we can rule out that possibility (that it interfered).
If it matters, both TVs and both NESes are/were PAL.