1986 and 1990 Honda Civics: a PITA: just no space to turn a wrench in the engine compartment. Replacing a radiator took an absurd amount of time (and oh my aching back!)
1998 Toyota Sienna: replacing the radiator (w/engine cold) took 30 minutes the first time, 15 the second and third. My 13yo son displayed some interest so we did it an extra time :-). Changing the rear-cyl-bank O2 sensor (wedged against the firewall and crossmember) was a PITA.
1995 Camry w/same V6 engine as above Sienna: changing the same rear-bank O2 sensor was a breeze (bigger engine compartment).
Access is the key.
BTW I own two 1973 Toyota trucks, bought because they're simple to work on and exempt from CA smog testing (points ignition might survive the anticipated solar EMP!). And I agree that working with carbs is a black art with minimal feedback available, and EFI (real-time feedback!) is a major advance. Maybe EFI engines will "find their way" into these trucks :-)