It really depends. For photos, the WCG support of the higher end iPads really makes a noticeable difference, but you may not notice it if you haven't seen it regularly. Similarly, non-WCG video streaming can be excellent, but if you add WCG to the mix it's even better.
Is it worth spending hundreds more for this incremental improvement? For many people no, but once you're used to it, it can be a big deal for some people. Plus the higher end iPads have other benefits such as more RAM, ProMotion, better speakers, better cameras, better SoCs, etc.
I for one probably will not get another non-WCG iPad for myself any time soon. Yes, Apple has me over a barrel.Then again, my main TV at home is a 65" OLED with HDR and Dolby Vision, and I frequently watch 4K HDR content, from its build-in 4K apps, from my 4K UHD Blu-ray player, and from my Apple TV 4K.
I hear you and what you say makes sense. But I don't feel I'm missing anything by not owning a significantly more expensive Pro model even with WCG.
From my perspective, buying the regular iPad more frequently at significant cost savings allows me to overcome any performance issues such as RAM or processor limitations by simply buying the next generation a lot sooner. I really don't want to invest heavily in a tablet that is so limited in life technologically, let alone in battery life. It is, after all, really a temporary mobile device unlike the more permanency of a desktop.