Even if you divide up the responsibilities in football, on any given play you’ve got to be watching for

Illegal shift
False start
Offsides
Play clock
Too many men on field/break huddle
Allow for defense to sub
Holding
Pass interference
Illegal touching
Grounding
Facemask
Chop block
Catch or no catch
Down and distance
Etc etc

And you have to do it on a huge field with a mass of 22 guys running around at full speed

In basketball you have 3 dudes watching for fouls and who touched it last before going out of bounds.

It boggles my mind basketball refs consistently are so bad.