people said this on bitcoin from it's beginning and some are saying it today.If you check who is saying it is a scam you will see their interest.mass of entries to their sites and earning from it.After two years, none of the accusations were true regarding the company.
Decentralization is from governments and central banks.
Bitcoin faces challenges because it is open source and needed changes to adjust.A company can do this faster and easily.
Last thing- a scam won't attract people like this one:
https://www.onecoin.eu/uploads/media/default/0001/01/7a76e713fcfcae22281da1b94ce69c2485bf594a.pdf

Hope it is an answer for you, and thanks for "onecoin" on his.