I had very similar concerns. The thing is, the iPhone 8 Plus is a perfected phone. It's the result of three-four years of trial and error. It feels super polished to me. I can't say that of my 7 Plus.
Being an Apple fangirl (sort of), I did contemplate getting the iPhone X, given that I do enjoy OLED screens. But other than the OLED screen and a new body, there's little it has going for someone like me who values solid design over the latest and greatest for the mere sake of it. I don't need to brag and show off that I can afford something. I did not buy the iPhone 8 Plus to serve as a status symbol. I bought it to be my daily driver, my extended hand. The iPhone 8 Plus excels in being just that. To top it off, it sports a now "classic" design that I see as iconic. I love the look and feel of this "outdated" device, love the thick bezels (OMG, right?) to rest my thumbs on while using it in landscape mode.
If I want something that has useful features that my 8 Plus doesn't have, e.g. a pen and other nifty productivity stuff, then it certainly isn't the X at this time, I'd be looking at the Note 8 or other phones by various manufacturers.
The X and 8 Plus are extremely similar in features, too similar to even be worth noting the differences. The biggest difference is that the 8 Plus doesn't have the "wow" factor. It isn't new, it isn't exciting, and it isn't the latest. For people who need just that, yeah, I can see how the iPhone 8 Plus seems like a horrible choice at a similar cost.