Here is one abstraction that definitely outlived its usefulness
Threads
They aim at abstracting a processing unit. They were very useful when processing units were a scarce resources, to the point there usually was only of them. Their usage was to allow sharing of that scarce resource.
But at a time where we may have them by tens or hundreds (or even more for the most radical proposition), they are just an impediment we need to ge rid of.

Threads were the training wheels on our bike,

it is time to grow up and dare ride without them!