Funny, the one thing you highlighted that "hamstrung" the current-gen is the one thing thy dint change when they had their mid gen refreshes. Kinda suggests that you are a little off on what you are saying.
Well it is easy. Once
the weakest link is set for all multi-platform games, it defines the whole gaming experience, design wise (for art, mechanics, animations... etc. you name it). So, if you are making a multi-platform game then you are hamstrung by a bottleneck which is always guaranteed to be the consoles and some part of their specification within (namely their CPU architecture). The mid gen refresh resulted in overclocked APUs in the CPU side, but they couldn't make it a new microarchitecture without compromising the base versions of the consoles. So all the multi plat games were designed with these in mind. So, what I'm saying is true when you keep in mind that console manufacturers couldn't radically change their CPUs, so they at least Overclocked them.
An example I could give that might change your mind is PC-only Star Citizen, and how it is literally impossibly to port the same game to current gen (base or enhanced), since the game is designed from the ground up with high end and enthusiast PCs specs in mind, so there is no porting, it is specifically made for PCs and their SSDs and high TF GPUs and really fast CPUs that can feed those GPUs.
Well on the other hand console exclusives could also prove how they can eke out even the last bit of performance on a defined/set spec, but this still doesn't change the fact that they are easily bottlenecked somewhere and the whole design of the game depends on mostly hiding these or they are always designed from the ground up with those limits in mind.
Edit: A good example of an agreed limit can be found in Spiderman PS4 game where the maximum web swinging speed will be a set limit, so without any skill they make you start slower and with every speed skill applied, it automatically hits the limit at which the game assets can be streamed in and out of screen.
So that game with it's assets, crowd numbers, object details at different LODs, number of cars, number of high rises, the area of the neighborhood... etc. is all dependent on this design choice and a set limit. THEN came the Ssd demo where you can zip through the same city at blisteringly high speeds. NOW and only now it is possible to make the same game for Superman with all of the above quantities and qualities for every design choice. They may even make the neighborhoods large enough to scale to actually 1:1 (instead of shrinking them to a more possible sizes). They may make the crowds even larger, and THEN make them even more Interactive, so it is not just taking selfies with them, or high fiving, but also playing basketball with them, or saving a cat from a tree once in a while etc. They can make the same cars not go round and round but different, more diverse cars go in a simulated traffic that is affected by crimes .... All these are held back mostly by the CPU.
The mid gen refreshes in the current-gen don't exist because anything was holding anything back.... that's just a totally wrong statement, especially being that games are still made primarily for those 2013 boxes. Not the refreshed 2016/2017 boxes.
Well you actually you answered yourself with "games are still made primarily for those 2013 boxes. Not the refreshed 2016/2017 boxes." So, something was holding them back from playing at 4K (either with checkerboard, or native, or some other reconstruction) and the mid gen happened. They STILL play the same games, albeit at a higher resolution and/or with other image quality improvements, but everything else is the same. They couldn't make a different enough game (design wise) for the
enhanced consoles only even if the developers wanted to (not to mention it is stupid to segregate their user base right in the middle - and thus perhaps making it a forced generational leap).
Edit 2: The goalpost hasn't changed since the mid gen refresh, the resolution target is still 4K, so because of Zen2 it will either make it more performant 4K for everyone like at 60 fps or much more good looking at 30fps.
