The pace of older movies feels slower. In many cases it takes longer to tell the story. Most of the time a story is linear with fewer flashbacks and certainly not the current trend of starting with an action sequence then flashing back to exposition.

The older the film the greater the possibility that actors were trained more like stage actors. Method acting techniques evolved through Stanislavski to different schools including Strasberg, and Meisner. Throughout the decades acting techniques changed and that reflects in the performances over different decades.

Certain film devices and tropes were popular during particular decades. During the 70's and 80's lots of films had musical montages in them. Tropes change. Every teen film from 1980-2005 or so had a scene in a mall. Kids don't go to malls much anymore so it's not a trope in current teen films.

Most plots in old movies seem to depend on people not being able to access information or to communicate immediately with others in order to solve the problem the plot twists presents. The existence of cell phones would ruin the plot of many older films.

Many older movies depict characters who operate under norms regarding relationships that are considered disrespectful if not downright predatory in the 2020's.

Stock characters in many films, especially comedies in the mid-late 20th century often involved race and gender stereotypes that would be considered racist and homophobic now.

Action sequences look very different. The ability to move the camera with the actor changed a lot after the mid 70's with the invention of the steady cam. The use of stunt doubles required a different way to shooting action sequences. Not many closeups. With digital effects action sequences can look a lot more dangerous without endangering actors or stunt people. With older films, in order for scenes shot using mechanical effects to be somewhat safe there had to be a lot of cuts which sometimes lose continuity.

The evolution of digital effects is evident. People traveling in cars look fake in mid-20th century films. The way a scene looks when it's shot using mechanical effects vs digital effects is different. Scenes shot with actors on physical sets vs actors on green screens with computer generated after effects sets look different. I would argue that performances by the actors are affected by the environment in which the scene is shot.