Also the Internet nowadays became the most important part of global media and what is main thing about that, that it gave freedom of speech to society, not just to authorized people, such as journalists and politicians, how it was before.

Also the Internet nowadays has became the most important part of global media and the main thing about it is that it gives/has given freedom of speech to society, not just to authorized people, such as journalists and politicians, as it is used to be.

Если честно, ощущение преужасное... "What is main thing about that", "how it was before"? Кошмар... Пытаться переводить канцеляризмы буквально -- не стоящее занятие. Слишком много лишних слов... И потом, зачем писать одно длинное предложение, когда вместо него можно написать несколько коротких? Как-то так:

Also, in the recent years, the Internet has become the most important part of the global media landscape. This is extremely important, because it has given a voice to the common citizens, not just those in the government and official media.

А по существу вопроса -- святая наивность... Интернет -- это средство распространения информации. ЛЮБОЙ информации, включая пропаганду, наглую ложь и честные ошибки.

Например, Nowadays it has become a tradition to be with the family on New Year's Eve.

Past Simple это, как правило действие, которое происходило в прошедшем времени и там же оно и закончилось.