Yeah this is probably my major peeve about films and TV (along with swords as lightsabers cutting through armor). It turns out, our ancestors really didn't like dying and would do things to prevent it, such as making sure you know who's behind you and on your side. Running, too. Formations would walk into each other slowly because throughout history, battles were giant games of chicken where the first person to lose their nerve gets stabbed.

Moving in an orderly fashion where you can avoid getting stabbed in the back, avoid running out of breath, and know what everyone on your side is doing is much, much more effective than using your face as a battering ram to headbutt the shields of the other side.

Then there's the whole getting trampled to death by 2,000 pound animals (or bigger, like that time Hannibal crossed the Alps with African elephants). Standing in a block and making a wall of knives is the easiest way to avoid getting body slammed by a horse.

The Last Kingdom actually did a pretty good job with this. Most battles are just a bunch of dudes forming shield walls and stabbing at each other waiting for calvary to break the other side's formation.

They have sequences where the main guy does superman shit, but the rest of the guys are all packed in tight and holding a line.

the only times formation fighting at scale has been convincingly done on film was when warsaw pact countries lent heaps of soldiers to film productions. the "average hollywood film" is less choosing the spectacle of dudes duelling over formations and more appreciating that if you zoomed out sufficiently the audience is going to realise there are 200 dudes in this field pretending to be 20000