Not that this was directed to me, but you couldn't be more wrong.
One example of why that claim of "timeless perfection" is a problem is that it gives ISIS really strong ground to stand on.
ISIS isn't really on a strong ground, actually they are on a no ground at all. And "timeless perfection" is not the problem. The problem is something you were advising and promoting, that is cherry picking from the Quraan. What ISIS does is taking two words of a set of verses and putting them outside their context. Let me provide you with an example.
2:190 Fight in the way of Allah those who fight you but do not transgress. Indeed. Allah does not like transgressors.
2:191 And kill them wherever you overtake them and expel them from wherever they have expelled you, and fitnah is worse than killing. And do not fight them at al-Masjid al- Haram until they fight you there. But if they fight you, then kill them. Such is the recompense of the disbelievers.
2:192 And if they cease, then indeed, Allah is Forgiving and Merciful.
2:193 Fight them until there is no [more] fitnah and [until] worship is [acknowledged to be] for Allah . But if they cease, then there is to be no aggression except against the oppressors.
2:194 [Fighting in] the sacred month is for [aggression committed in] the sacred month, and for [all] violations is legal retribution. So whoever has assaulted you, then assault him in the same way that he has assaulted you. And fear Allah and know that Allah is with those who fear Him.
If you look at the conditions to fight those than you will find.
1- They are the ones who started the fight.
2- They transgressed,.
3- Third they are the ones who expelled you out of your home.
4- Regardless of all that, if they stopped, you have to stop too.
Are these 4 reasons enough to fight back or not? If the answer is no, than your mentality would have probably seen Hitler ruling the world.
Of course, what ISIS does is that out of these four verses they would only take the "And kill them wherever you overtake them" part and disregard the whole context to justify that these actions are Islamic. This action is not only done by ISIS, it is done more and more by islamphobes and those who promote hating Islam.
They also disregard many verses such as the following:
60:8 Allah does not forbid you from those who do not fight you because of religion and do not expel you from your homes - from being righteous toward them and acting justly toward them. Indeed, Allah loves those who act justly.
See not only we can talk to non believers, in deed we should be righteous to them if want God to love us. Not the last word of the verse, "Justly". Do you see any just in ISIS actions?
So when you ask Muslims to cherry pick, know what you are asking for.
Islam is a complete and perfect way of life when taken as a whole.
I am sorry that you have a problem with the word "perfect" and you don't believe in perfection, but God is perfect, and he surely provided us with a way to live our life. It is out there for us all to search for it. And if God is perfect than His way is perfect also.