I used to have the 135/2.8 Ai and loved it for its compactness and sold it for very little money when I got the D70 as I felt Nikon would not support non-CPU lenses in my price class of camera body. However, they added non-CPU support in the D200 so then I've reacquired some manual focus lenses. I feel the D7500's removal of this feature sends just a confusing message - Nikon used to be proud about their lens compatibility now they've made a confusing mess of it. They've introduced AF-P lenses that seem to autofocus superbly in live view on compatible cameras but few cameras support them. I think my issue with this is that we cannot trust Nikon to hold compatibility or be consistent about it. And with lack of trust it becomes difficult to make an investment in the gear. I do not think manual focus lens use is that uncommon - there are no records of who owns and uses second hand gear and on which camera bodies. I know quite a few people who like to fish bargains online and manual focus metering support matters to them. In my opinion Nikon should provide stopped down metering support on the D7500 in a firmware upgrade. There is no disadvantage to providing it and it can help people, e.g., when using a macro bellows setup (a perfectly legitimate application for a DX camera that supports electronic first curtain shutter). The D7500 does not meter with manual focus lenses that do not have a CPU. There was a specifications error originally on Nikon's pages that suggested there would be metering but they fixed the error.
There
are records of how many people are using Ai and Ai-S lenses: market price. If the lenses are bargains that means demand is low relative to supply.
As of right now Nikon say the D7500 is "Compatible with AF NIKKOR lenses, including type G, E and D lenses (some restrictions apply to PC lenses) and AI-P NIKKOR lenses and non-CPU AI lenses (M mode only); IX-NIKKOR lenses, lenses for the F3AF, and non-AI lenses can not be used". What they say for the D7200 is "Compatible with AF NIKKOR lenses, including type G, E and D lenses (some restrictions apply to PC lenses) and DX lenses, AI-P NIKKOR lenses, and non-CPU AI lenses (A and M modes only)". So the D7500 has lost aperture priority with non-CPU lenses; it has
not lost metering. You just have to use manual mode. And worst case all you have to do is use a light meter.
It is inevitable that there will be
some limit to backward compatibility, and there always has been. Pre-Ai lenses cannot be used on digital, and G lenses cannot be used on the FM3: how come those things never made you doubt the wisdom of committing to Nikon but limited automation with Ai-S lenses on the D7500 does? The level of backward compatibility Nikon is providing with the D7500 is high, by camera industry standards - let alone any other technology-based industry. Can you mount any pre-1987 Canon lens on any Canon digital camera? No. (And that was the 3rd time Canon abandoned a mount, because the EF replaced the FD, which had replaced the FL, which had replaced the R). Can you mount any Olympus OM manual focus lens on any Olympus digital camera? No - unless you buy the adapter, and you have to stop-down meter, and as of today the adapter is out of stock at Olympus (
https://getolympus.com/mf-2-om-adapter-om-to-micro-four-thirds-lens-adapter.html). And then there is Sony.
There are lots of things that are presently found only in higher-level cameras that you or I might like in lower-level cameras - a dedicated AF-On button, in my case, eg. There are also lots of things that you or I might feel would be no loss if they were only found in higher-level cameras - a tilting LCD, in my case, eg. The fact that they might be easily or cheaply included is really beside the point, because for every person who would value a dedicated AF-On button or a tilting LCD or aperture priority with Ai-S lenses there will be someone who would regard that feature as futile expense.