May peace be with you.
Even if one takes the group of people that the Quran refers to as
'mushrikeen' and notes how they made
partners with God (28:64, 53:19-20), one can quite convincingly derive an understanding of
'shirk' as any association with God, ascribing partners or partnership with Him (the act of
'sharik').
There are numerous other verses in the Quran which support such a definition of 'shirk'.
It is arguably in the ambit of
'kufr',
[1] where shirk will not be condoned. This is when the errors of ones ways are made absolutely clear to one and they still refuse to accept guidance and continue with their erroneous ways.
It is in this scope of inexcusability that verses such as 4:48 and 4:116 should be arguably understood.
Therefore, I would have to strongly, yet respectfully disagree with your statement:
To the best of my understanding idol worship is NAJIS and not shirk.
With utmost respect, in my view this statement has no warrant from the Quran as I have attempted to demonstrate above when attempting to define 'shirk' from a Quran's perspective which includes the worship of idols.
Furthermore, many Muslims incorrectly assume that idol worship is restricted to worshipping statues or simply attributing other Gods with the Lord Almighty. Although statue worship and attributing other forms of deities with God is no doubt a form of idolatry, limiting it to this understanding is untenable from the Quran's perspective. Idol worship from the Quran's perspective can take many forms. Please see article
[2] below.
I hope this helps, God willing.
Joseph.
REFERENCES:[1] UNDERSTANDING 'KUFR' (DISBELIEF) FROM A QURANIC PERSPECTIVEhttp://quransmessage.com/articles/understanding%20kufr%20FM3.htm[2] IDOLATRY ACCORDING TO THE QURANhttp://quransmessage.com/articles/idolatry%20according%20to%20the%20quran%20FM3.htm