Worship of Mary:https://bible.org/question/should-we-worship-mary
While all Roman Catholics do not necessarily worship Mary, the fact that many pray to Mary (which is an act of worship and no where justified in Scripture) and give her titles which resemble those given to Jesus Christ including the idea of mediatorship.
Worship is something that is to be restricted to God alone.
As the angel stressed when John fell at his feet in appreciation for the revelation he had seen and received, “Do not do that; I am a fellow servant of yours and of your brethren the prophets and of those who heed the words of this book; worship God” (See Rev. 19:10; 22:9).
Mary is not God and her exaltation in the Catholic church has no foundation in Scripture.
While we may and should appreciate the ministry of men and women, they are only instruments used of God for His glory.
Christ alone is our mediator.
Paul clearly points this out in 1 Timothy 2:3-6.