With AI picture enhancement it very much depends on the original content. You can get some really amazing results from grainy and slightly soft focussed pictures. It's also very good for colourising black and white pictures and seems to guess the correct colours more often than not in my experience. What it can't do is put detail back that there is next to no indication of in the original , instead as you say , it will just remove it and maybe replace it with background. Lattice towers against a bright sky are especially prone to this in old pictures of radio ships. Many of the pictures of the Mebo 2 are sadly like this but this technology is advancing at rapid speed and will be improved even further.
I have some pictures which were just a bit grainy and soft of the Communicator from when Laser first started and also the Ross revenge and the results are extremely good looking like they had been taken only yesterday with a modern camera.
There is some impressive AI software for enhancing video footage that was shot on old video tape which is starting to get more out there and does a great job on classic TV shows and so could be used on those fuzzy camcorder VHS-C films from the old radio ships mainly from Laser and Caroline in the 80's.
There have been a lot of examples of vintage film clips from as much as a century ago so the very earliest that exist of city scenes from flickery and jerky black and white silent. This is of London from 1943 and I find this sort of stuff fascinating.


Sorry, this has drifted a bit off topic.