I realized that many tasks had nothing to do with the goals, but it was no big deal.

But it was no big deal.

This is a very normal phenomenon in our company because the yearly goals are mostly used for the boss’s reporting.

Because the yearly goals are just used for the boss's reporting.

RThe culture in our company is to report whatever needs reporting and do whatever needs doing is the culture of our our company.

I looked back on this year's goals and the tasks I had accomplished.

"had' is not wrong but not needed

I realized that many tasks had nothing to do with the goals.

Here, "had" is needed.

But it was no big deal.

You could put this sentence in the present tense to show it is related to the generalizations you make in the sentences after it.
(The fact that it's no big deal is part of the corporate culture)

Because the yearly goals are just used for the boss's reporting.

The grammar police may not approve of this sentence. They will say that starting with "Because" makes this a subordinate clause, and they will tell you to put a comma after reporting and add a main clause, or delete "because." However, in this personal reflection about your dissatisfaction with the company's culture, it seems appropriate; and I don't think an editor of a work of fiction or a blog would ask you to change it.

Report whatever needs reporting and do whatever needs doing is the culture of our our company.

So, the company's efficiency is really worrying.

Efficiency or lack of efficiency? Is efficiency the best word here? Is it clear how the reporting is related to the company's efficiency?
I am not familiar with the corporate world, and I don't understand exactly what you mean, but that may be due to my limited background knowledge rather than your text.

It's already the tailmost the end of 2025.

Not much people uses “tail end”

Report whatever needs reporting and do whatever needs doing— this is the culture of our our company.

— is unnecessary but it improves flow of thoughts