The bible mentions that not everyone who says Lord Lord will enter His kingdom. I agree with you when saying this refers to people who are not 100 % believing on the price paid by Jesus Christ on the cross, but I get really confused when this statement extends to people who were prophesying, casting out demons and healing people. Do you want to tell me that there are people who are given a gift of healing, prophesying and casting out demons but not 100 % believing on the Lord?
It’s important to understand that not all miracles come from God. In addition to Matt. 7:21-23, read 2 Cor. 11:13-15, and 2 Thes 2:9. These passages tell us that it isn’t just people who don’t rely 100% on Jesus who do these things. Some of it is the work of Satan and his ministers. For example, someone who appears to demonstrate gifts of the Spirit and then teaches false doctrine can not be walking with the Lord. “No good tree bears bad fruit, nor does a bad tree bear good fruit. Each tree is recognized by its own fruit. People do not pick figs from thornbushes, or grapes from briers.” (Luke 6:43-44)
It’s our job to search the Scriptures to see if the things we’re being taught are true (Acts 17:11), even if they’re accompanied by the appearance of miracles.