Polytheism

Polytheism is the worst injustice because it is the origin of all major sins and it is denying the greatest Truth. Murder is a major sin which leads to hellfire. Those commit such crime do not remember Allah while coming their crime. Faith in Allah protects from crimes, and denying Allah's existence opens satanic thoughts and act.

Wassalam.

Allah is The Absolute Just, Merciful and All Knowing. He never punishes those who do not know the religion of Islam. He said in Quran : We never punish any one till We send a messenger وما كنا معذبين حتى نبعث رسولا (Sura 17, verse 15).

Those who did not know the message if Islam and died on that ignorance will be given a full chance in the Day of Judgement to know then will be given full option to think and decide then respond. 
The Justice and Mercy of Allah will never allow punishing any one before providing him full chance of knowing and deciding with his free will.

'Wassalam.

Allah (SWT) created all His creatures for showering on them His countless bounties and unlimited Mercy. We read in Qur'an:  (Except those on whom Your Lord Has bestowed His Mercy, and for that He did create them). (Sura 11, verse 119).

Allah never created people to send them to hellfire, except those insist on criminal acts and continue committing injustice and die on such criminal acts.

Allah, The Most Merciful, The Most Compassionate gives every human being thousands and thousands of chances to believe in thr Truth and do good then enter the Paradise.

Allah (SWT) Has promised every one who believes in Him as The One God to go to Paradise as the Prophet Muhammad (SAWA) said: Paradise is the ultimate place for all believers in Allah الجنة للموحدين.

It is not correct the think majority of people since the time of Adam were atheists or non believers. Majority of human beings are believing in The One God which is part of the instinct knowledge even if the cultures and titles are different.

'The Mercy of Allah is much more greater than what we think and He will deal with His creatures with His great Mercy except the enemies of Allah.

'Wassalam.

Polytheism شرك is to worship with Allah some one or something else. Those who did polytheism in the past then left it and became Muslims will be forgiven because they have left polytheism, but those who insisted on polytheism and died  with it, will not be forgiven as you read in (Quran 4:48).

Wassalam.

Allah (SWT),The Most Merciful, The Most Just,  knows who is entitled to be in the Hellfire. We are read in Quran that the enemies of Allah will remain in the Hellfire as they were insisting on doing wrong forever.

We should not waste our time in searching what will happen to others, rather trying our best to save ourselves from bad deeds and sincerely doing good in faith and practice to be with the Righteous in the Paradise.

Hadeeth says: The Paradise in the ultimate place of the believers in Allah الجنة للموحدين 

Wassalam.

If you repeated the wrong words of others with out intention of its meanings of Shirk, you are not a Mushrik. Your faith is what is in your heart. Still you need to repeat Estighfaar for saying something wrong.

Wassalam.