Shirq

The most important and fundamental point which differentiate between a mushriq and a momin is Niyyat [an intention] not the act. Niyat can only be judge by the Almightly not by any human [thanks God for that] no matter how pious is he/she.

thats why its a founding principle in religion is

"innamal a'malu binniyat"

for example if i prostrate to kaba with a niyat that Kabah is the almighty then i am mushriq but if do the exactly same act with slightly changed Niyat then i a momin.  and who can judge my Niyat when i was prostrating , none except the Almightly.

Prostrating to Human.

Sahabah did prostrate to the prophet [Peace and blessing of allah be upon him and his progeny] but prophet [Peace and blessing of Allah be upon him and his progeny] never said that they are mushriq or even Kafir he even didnt asked them to re-certify their faith. but he said not to do that. 

Previous Prophets used to do Prostration to Human as a mark of respect , because the niyat was a mark of respect rather than 'concept of being almightly' thats why i wasn't a shirq.
Allah has ordered Angle to Prostrate to Adam [AS]  was that a shirq, you might think yes, but as Allah and the Angles didn't consider Adam [AS] as an Almighty.

but nizam sb i don't think its their mistake , because if you ask a carpenter to fly a plane or a barber to do surgery on you, or a military man to run your country or a Dr or singer or an actor to teach you religion the results will the same ie a complete disaster