My take as one who now lives in Czechia: it’s a great place to be an atheist. It is one of the most secular countries in the world; most people are atheists or agnostics and publicly saying you’re not religious or even criticizing religion (within certain bounds of civility) is socially acceptable. Those who are religious tend not to be particularly devoted to practicing religion.
On top of this, atheism is actually protected by the constitution. Specifically, in Czech law, the right to freedom of religion is referred to as “freedom of confession.” Per Article 15, Paragraph 1 of the Charter of Fundamental Rights and Freedoms: “Svoboda myšlení, svědomí a náboženského vyznání je zaručena. Každý má právo změnit své náboženství nebo víru anebo být bez náboženského vyznání.” (my emphasis)
My translation: “Freedom of thought, conscience and religious confession is guaranteed. Everyone has the right to change their religion or to be without a religious confession.”
It is true that some of the main national holidays are originally religious ones: Christmas, Easter, St. Wenceslas’ feast day, the feast day of Sts. Cyril and Methodius, and the day of the burning of Master Jan Hus at the stake. However, no one pushes going to church on that day. Many people restrict themselves to observing the days in secular ways (and there are quite a few non-religious traditions associated with Christmas and Easter). Moreover, the last two named holidays (which are back to back on 5 and 6 July) and that of St. Wenceslas’ Day have historical backgrounds that transcend religion (Sts. Cyril and Methodius brought not only religion, but also greater literacy to Great Moravia, an ancestor state of the Czech lands; St. Wenceslas - the Good King Wenceslas of the carol - was an early Bohemian duke, and Jan Hus a religious reformer whose teachings started a Czech form of early protestantism that had a major impact on Bohemia’s orientation in late Medieval and later European history).
Religion has had a great impact on society and culture. A lot of customs and symbols have some origin in it. Think of all the flags with crosses on them that have become distinct and recognizable national symbols (the UK, Switzerland, all the Nordic countries, and so on). The expression “Good bye” comes from “God be with ye.”
I would be more concerned if there were things like state-sponsored prayers, but see, the Czech Republic is pretty much completely free of this. I have never been present somewhere where there was a state-sponsored prayer, with the exception of some minor local WWII-themed memorial services where there was a military chaplain present.
This country does maintain a register of officially registered religious denominations, which gives them some rights (such as officiating at legally-binding wedding ceremonies), but according to the Constitution, the religious groups carry out their operation independently of the state and the state must not bind itself to any ideology, including religious ideology.
During Communism, approved churches were overseen by the state, and for some time after, they were actually sponsored – and ministers of religion given a salary – by the state. This was the case when I first came here in 2003. However, since then, a law has been passed to phase this system out.
All things considered, in the Czech Republic, the practice of religion is something that you and only you decide how much you will involve yourself in it.