I shot plenty of pix in the 80s and have NO recollection of a specific blurry look. The fashion at the time was sharp as a tack edges, bright, clear color and crisp printing. What you may be seeing are aged prints that get muddy in time (regardless of era). The lenses were capable of very sharp images, even the cheap lenses were better than a lot of the kit lenses available now. Most people also understood ISO and realized they had to use faster film in lower light. Again you may be seeing grain, which on faster films could soften edges within the image. This especially happened on the very high speed films (and still does, it is a technical aspect that must be dealt with on the aesthetic level.)
The lack of image stabilizing lenses did not impact the art form in general. Specifically yes, once IS was released, we could shoot out of helicopters without gyroscope mounts, and that did make life easier, but how often does one shoot out of a helicopter? Wildlife also got a bit easier as you could handhold and thereby move more quickly. All that notwithstanding, people still got great images out of moving helicopters, planes, of animals in motion. It just required work, practice and a good eye.
Background blur is a function of depth of field. Set the aperture to a low number and you'll get the background out of focus. Make sure the shutter speed is set to match. Use the light meter.