Older ones are newer ones are not.
However if the mower has suddenly gone bad, then it will not be a problem with the adjustments.
When a carb is going out of adjustment, it happens slowly over time.
Have a good look at the governor spring, I will guess that it is hanging up on something.
The anchor point at the other end of the throttle cable could also be loose.
Get down and try to move the throttle lever by hand.
If the engine can throttle up & down quite OK when manipulating the lever by hand then the carb is fine & the problem is in the controls.
And of course the inverse applies.
A lot of damage to perfectly good carbs is done by people "fixing" ones that were not broken.