In a world where the Bible is "open for interpretation", and even so-called Christians are calling for inclusivity and to let everyone "live your truth", it seems very alien to take a solid stance on any Biblical issue. Certainly to the extent of saying those who oppose it are actually sinning. This seems like the best way to endure accusations of divisiveness, and even bigotry.
Realistically, however, we do have to draw some lines. After all, Christ Himself would often rebuke people for disagreeing with certain interpretations of Scripture. The Sadducees, for example, did not believe in an afterlife. Yet, Jesus' reply to them wasn't "that's ok, you live your truth", it was "You are mistaken, not knowing the Scriptures nor the power of God." (Matthew 22:29). Jesus would very often threaten the Jews of His day, telling them things like "Moses accuses you to the Father" (John 5:45).
So, clearly, it's not enough to just have a Bible and interpret it any way you see fit. There is a right way, there is a wrong way, and the wrong way can be anything from a sin nailed to the cross of Christ to a one way ticket to eternal damnation.
With this in mind, we see that how we interpret Scripture, in particularly the books of Moses, matters. To be clear, I am not saying the doctrine of Creation is so vital to the Christian faith that to err is to cease to be Christian. It's a non-essential issue, and so just as no one loses their salvation for believing, for example, KJVOnlyism, no one is ripped from the hands of the Son just because they are so deluded as to believe their distant cousin is a chimpanzee.
Nevertheless, the Bible makes it abundantly clear, and both Jews and Christians have strongly contended for millennia, that we are, in fact, literal descendants of the historical Adam and Eve, who literally were created specially on the actual 6th day of history, roughly 6,000 years ago. Furthermore, it follows a real genealogy from the literal Adam to the Literal Noah, who survived a literal, Global flood, and whose descendants were dispersed from a very real Tower.
This is what the Bible teaches. This is so unbelievably clear that it could not reasonably be made more clear. This is prominently displayed within the first 8 pages of the average Bible. It is a repeated theme throughout the rest of Scripture (even being foundational for various other doctrines). And the Church has traditionally maintained all of this so that even those lacking the diligence to pick up the Bible may be made readily aware of it just by attending a Biblically minded congregation. There really is no excuse to not know the doctrine of Creation, both what it teaches, and that what it teaches is correct. When you question the truth of creation, what you are actually doing is questioning the truth of the word of God.
And this is precisely what Old Earth beliefs were designed to do! Mankind didn't make up silly stories like these for fun. They have purpose. That purpose, in the words of Charles Lyell, is to "free the science from Moses".
Some compromisers object, stating that the Bible was never designed to tell us the age of the Earth. Of course, to an extent, this is true. It's certainly not the primary message of any section of Scripture. But there are three problems.
The first, and most obvious, is that the age of the Earth is simply the smallest element of Evolution. Of course, if you want to say the Bible is true, it's just that Adam was created 16,000, 60,000, 600,000 years ago, instead of only 6,000, that's still a problem, but it's relatively tame. But Evolution is an atheistic creation myth. Evolutionists are rarely able to affirm Genesis 1:1, much less the rest of Genesis 1-11. A Theistic Evolutionist is only able to affirm Genesis 1:1 as a side note, and will have to mince and mash the rest of the chapters, as well as future allusions to them.
The second is that regardless of whether the Bible was designed to tell us the age of the Earth, it does so anyway. It does this through the genealogies of Adam, right the way up to Christ Himself. 2,000 years (from now, back to Christ) + 4,000 years (from Christ back to Adam) + 6 days (from Adam to the beginning) = 6,000 years, give or take. Thus, eventually you have to deal with the genealogies. The attempts Old Earthers make to do so are, to be as kind as possible, pitiful.
The third problem is that Satan picks up on those two points. He knows Evolution needs a massive history to work, and he knows the Bible precludes such a large history (plus he was there, so he has first hand knowledge about what actually happened). Thus, even if all the Bible does is imply the Earth is 6,000 years old, he can cast doubt on its authority by attacking the implication.
Think of it this way: If Genesis 1:1 says "In the beginning God created the heavens and the earth", the point of the verse isn't to tell us there was a beginning (and therefore, contrary to the assertions of philosophers in the past, the universe is not eternal), but it can be used as such. The flip side of that coin is if the devil can convince us the universe is eternal, that makes Genesis 1:1 wrong.
You see, then, that even Old Earth Creationism, which is not necessarily the same as Theistic Evolution, is problematic. Theistic Evolution itself is basically saying "lump what the easiest book in the Bible says, the atheists are 100% right about where we came from, and God Himself cannot convince me otherwise". There has to be a point at which we can look at a worldview and say it's not just a matter of minor error. If we, as Christians, cannot look at such blasphemous views as a sin, we may as well just burn our Bibles and do what is right in our own eyes. All of God's people, armed with the most basic Biblical knowledge, need to call this utter heresy out for what it is, drop its rotten corpse back in the devil's hands, and tell him it's not fit to be in our churches, or our hearts.