A Question related to the method of find lower bound : Trivial lower bounds

In Trivial lower bounds we just need to count the number of items in the input that needs to be processed and the number of items that need to be generated and the trivial lower bound time is then the sum of these two found numbers. My question is , we know that the time complexity = number of times the basic operation is repeated as a function of the input size * the time it is taken to preform the basic operation once. So as we can see from the formula of the time complexity that it depends on the basic operations not on the number of inputs and output items. So how does the trivial solution is used to compute the lower bound ( worst time complexity of best algorithm) then ?