God's Word is what stands. And when you decide in your [un]"renewed mind thinking" that you can change what is written in Rom 12:2 because you "don't see a contradiction", that is not proper workmanship. We can't mix our thoughts/ideas in with God's Word and conclude we still have God's Word. We don't ... all we have is man's reasonings.
The "renewed mind thinking" believer takes God's Word as written and casting down imaginations and every high thing that exalts itself against the knowledge of God, and bringing into captivity every thought captive to the obedience of Christ (2 Cor 10:5).
The point is we do not realize there is a difference between the "renewing" of Rom 12:2 and the "renewed" of Eph 4:23 because we read the words in english. In english, "renewing" and "renewed" appear to be the same thing with the exception of the suffix ["ing" and "ed"].
We do the same thing when we read the word "love" in Scripture without understanding that there are different Greek words which are translated into the english word "love". Example: In John 21:15-17, two times Jesus asked Peter if Peter loved [Greek agapao] Him and Peter answered that he loved [phileo] Jesus. the third time Jesus asked Peter, Jesus asked him if he loved [phileo] Him and Peter replied that he loved [phileo] Him. Without understanding the nuances in the Greek text, we would not see the difference. And it behooves us to search out these truths in order that we might come to a more perfect understanding of the Word of God.
Without looking at the Greek text, we would not know that there were two different words used in Rom 12:2 and Eph 4:23.
Below is from Vines Expository Dictionary:
Renew/Renewing:
(Strong's #342 — Noun Feminine — anakainosis — an-ak-ah'ee-no-sis )
akin to A, No. 1, "a renewal," is used in Romans 12:2 , "the renewing (of your mind)," i.e., the adjustment of the moral and spiritual vision and thinking to the mind of God, which is designed to have a transforming effect upon the life; in Titus 3:5 , where "the renewing of the Holy Spirit" is not a fresh bestowment of the Spirit, but a revival of His power, developing the Christian life; this passage stresses the continual operation of the indwelling Spirit of God; the Romans passage stresses the willing response on the part of the believer.
(Strong's #365 — Verb — ananeoo — an-an-neh-o'-o )
"to renew, make young" (ana, as in No. 1, and neos, "recent," not different), is used in Ephesians 4:23 , "be renewed (in the spirit of your mind)." The "renewal" here mentioned is not that of the mind itself in its natural powers of memory, judgment and perception, but "the spirit of the mind," which, under the controlling power of the indwelling Holy Spirit, directs its bent and energies Godward in the enjoyment of "fellowship with the Father and with His Son, Jesus Christ," and of the fulfillment of the will of God. The word is frequent in inscriptions and in the papyri.
As far as the usage of the two different words ... in Rom 12:2, the emphasis is on the transformation which takes place in the life of the born again one as the renewing of the mind takes place ... and this must occur before we can "put off" the old man in order that we are renewed in the spirit of our mind so we can put on the "new man". Please note that the letter to the Ephesians is written to those who are faithful in Christ Jesus (Eph 1:1). The transforming by the renewing of the mind of Rom 12:2 works to our being faithful in Christ. Those who are faithful in Christ are instructed to put off the old man, be renewed in the spirit of the mind, and put on the new man (Eph 4:22-24).
Sometimes, it is good to ponder and meditate upon verses and allow God to work in our hearts to bring increase so we understand what He wants us to know ...