My OLEDs (plural) are fine. I buy 4K that is worth the upgrade. I have sold several 4K discs that I consider to be of poorer overall quality than the upscaled blu ray. You should compare Interstellar 4K and blu ray side by side.
I can understand a comment like ‘I buy nothing but 4k’ if you’re just starting out, but if you have hundreds of blu rays then a 4K disc has to prove itself. So when I watch a 4K disc and think ‘something’s not right here’ I look for answers. If you have the 4K and like it, good for you. For me, the upscaled blu ray is sometimes preferable, as the 4K has a green tint I dislike, and the space scenes were disappointing. There’s discussion on the internet about it.
I remember (no pun intended) Total Recall had some people complaining, others raving, depending on whether they had Dolby vision.
I’ve seen some old movies on 4K where the film grain is so pronounced I find it distracting. It may be technically superior to the blu ray, but the upscaled blu ray, on valance, for me, offers most of the benefits with few of the downsides.
There are many really good 4K discs. And for new releases, like Maverick, I have only watched the 4K disc. That’s now my ‘reference’, and I would have to look at the blu ray to see if the 4K is much better.