There's plenty of unscriptural beliefs and practices.
What is unscriptural
Shunning in totality
What it should be
Shunning only applies to the antichrist, who teaches that Christ did not come in the flesh. (2 John 7-10)
What is unscriptural
Everyone must preach and teach.
What it should be
Teaching is a gift of the spirit. Those who have that gift should use it. (Romans 12:6-8; 1 Cor 12:27-31; James 3:1)
What is unscriptural
Qualifying for baptism via a long series of study sessions and going over a bunch of questions
What is should be
When someone's belief and faith is strong enough and they have the proper desire to be baptized, who should say they are not qualified? The Ethiopian Eunuch was baptized immediately. (Acts 8:35,36) The jailer and his household were baptized that very hour of that very night. (Acts 16:30-33) Cornelius and his family were baptized once they received holy spirit (Acts 10:34-38).
What is unscriptural
Not baptizing in the name of the Father, the Son and the Holy Spirit. These words aren't even uttered during the baptism talk or actual baptism.
What it should be
Get rid of the whole identifying with an organization bit. Do it right. (Matt 28:19,20; 1 Cor 1:12,13)
What is unscriptural
Unbaptized publishers
What it should be
Anyone wanting to preach the good news can and should do so. (Luke 9:49,50)
What is unscriptural
Saying that one must become part of the organization to be saved
What it should be
Jesus said, several times, "come to me". (John 5:40; John 6:37; John 6:44; John 7:37)
What is unscriptural
Saying that only a small group should partake
What it should be
Everyone who follows Christ should partake. (John 6:53-59)
What is unscriptural
2,520 years prophecy leading to 1914
What it should be
Can't answer this. The 2,520 years prophecy is made up, insisting that Daniel 4 must have a secondary fulfillment when Daniel himself says the vision is fulfilled in Nebuchadnezzar.
There are so many more things... this is just off the top of my head.