There is nothing wrong with that isolator and it isn't an old one, this is current.
Joining the phone cable like that under floorboards shouldn't give you any problems, the scotch connectors are normally used outdoors too, i wouldn't worry about this. Putting a plastic box around this wouldn't make any difference, it would purely be cosmetic and being as you probably don't have your floor boards up all the while, quite pointless really
Joining the CATV cable in the way they have done in your picture, shouldn't give you any issues either. Not being able to see the whole picture it's hard to say, but they might have done this to enable you to remove the new piece they have added if you needed to for decorating or something like that????
That is just speculation however, as i don't know what your setup is.