I self-identify myself as a Protestant, and, in theory I agree with Sola Scriptura---the belief that Scripture is sufficient guide to what Christians should believe on things which are actually salient to Christianity. When the Holy Spirit moves to enable the full comprehension of what Scripture means, this works quite well. Unfortunately, this far too often seems not to be the case, and I find myself in sympathy with the more Catholic position that church tradition should be given a far greater weight.
I suppose one simply has to reflect that on many issues with theological significance, most of the church is presently at serious variance with the unseen church---that is the communion of saints reaching back to around 30 AD. Further, most Christians place far higher weight on current opinion then on the opinion prevalent in say, 100 AD, 500 AD, or 1500 AD. Further, one has to admit that Protestantism itself has schismed over and over again, to the point of being a frequent source of humor. It would seem that the Spirit animating many interpretations of Scripture is not in fact the Holy Spirit but a decidedly more malevolent one, or sometimes, perhaps no Spirit at all but simply a desire to find an interpretation that does not require the reader to be out of step with his peers and his age.
What can we do about this? Should we beg readmission to the Catholic Church, with it's more centralized approach to scriptural interpretation? Should we just pray harder? I can't answer either of those questions for myself, much less for any reader who happens to have dropped by for whatever reason. All I can suggest is this:
We must accept that our predecessors in the Church were at least as Christian as we are, in the aggregate. We must furthermore accept that they succeeded in spreading at least the knowledge of the Gospel to at least as great of a degree as we have. Furthermore, they have generally had a degree of understanding of the Bible at least as great as the average possessed by Christians today (a brief examination of the surveys of knowledge of Christians of the doctrines and beliefs of their faith will reveal this is a fairly low bar to meet). In many cases, they are far closer to the social circumstances in which the Bible was written and are closer to the source material than we were. For instance, how many of us have ANY concept of what living in a low-surplus society is like? Or what the accomodations needed to make such societies work actually are? I suspect that only a few modern Christians, likely those who have lived in very poor places of the world during long term missions have any grasp of this at all---and even then, they generally always had the option to move back---such privation was not a permanent state of affairs.
Given these premises, I would suggest this to anyone inclined to make pronouncement about how the Bible says that Christians should behave today.
Honestly answer the question, how would orthodox Christians from AD 500, 1000, 1500, 1750, and 1900 answer your question? If they all, or most all, agree with your position, you are probably right. Certainly each era has its errors, but as C.S. Lewis famously pointed out, they usually aren't the SAME errors. If most or all of them would disagree with you, the burden of proving that YOU aren't the heretic is pretty large. Smart as you might be, you probably aren't smarter than the collected wisdom and practice of your religion, and if you accept the premises of your religion at all, you must recognize that you are 'running on corrupted hardware' as the folks over at overcomingbias are fond of pointing out (in our neck of the woods, we call it original sin or total depravity, or simply failing to be a Pelagian heretic :-).
So let's take a hard case---slavery. Both Old and New Testaments talk quite a bit about it, probably because it was a fairly common part of the experience of a large fraction of the population. It isn't presented as an ineffibly evil institution in either Testament. Paul, in his letters to a slave and his master, doesn't even say the master should free the slave to the master. Yet in the 1700s, the church started moving strongly in the direction of condemning slavery and we take it totally for granted now that slavery is contrary to Christianity.
Why is this? Were the Christians who accepted slavery, serfdom and similar instruments of bondage wrong for nearly 1700 years?
I would argue that the key to understanding this lies in understanding the low surplus human society's condition. We are obscenely richer than anyone born before the 1700s. In a low surplus society, you simply can't afford to do a lot of things we take for granted now. In fact, you might not even be able to feed everyone. So what, in such a society, do you do with your screwups, idiots, and people who just can't fend for themselves? Your minor criminals that you can't afford to incarcerate and feed, your prisoners of war? The most merciful answer to that question is often bond-servitude, be it slavery, serfdom, indentured servitude, or the like. Christianity was not designed to only work in high surplus societies like our own, but in any society that God or Man might decide to inflict on us. Therefore it emphasizes that such servitude carries reciprocal obligations on the part of both master and slave (refer to Paul's various letters and the laws regulating slavery in the Old Testament). So why did it become considered an evil thing in the 1700s? Well, for that I suggest heading down to your local gym. Find yourself a fancy exercise bike or treadmill---one with a calorie consumption meter that will display in watts. You'll find that producing 150 watts is quite taxing, and the 6-7 hours that would be required to squeeze 1 Kilowatt-hour out of you very fatiguing indeed. Congratulations---you've just produced about 12 cents worth of power. This should drive home just how rich in terms of the power at our command we've become since the Industrial Revolution and the widespread availability of fossil fuels. Christians in the 1700s recognized that the amount of wealth available to society HAD FUNDAMENTALLY CHANGED as a result. Furthermore, Christians recognized that they had always been obliged to be as charitable as they could afford to be, and no more, and that said obligation had just enlarged along with their purses. Therefore they argued that society should no longer permit slavery.
Of course they didn't express it in many cases in exactly those terms, but it is telling that the timing is so close. Slavery generally ended in heavily Christian countries about as soon as society could afford to end it. Regretably, most abolitionists in the US didn't phrase their arguments in these terms. Had they done so, slavery might have ended in the US via a buyout similar to that in Brazil instead of via the bloodiest war in American history.