I’m familiar with your thoughts on how the games try and paint Mew as the ancestor of Pokemon and how backwards their logic is claiming it’s due to Mew having the DNA of all Pokemon. That, as you’ve pointed out multiple times, is not how ancestry works.
I wanted to share with you an idea I’ve had about how I’d handle the Mew situation and what your thoughts about it are. For me, since Mew is the only Pokemon barring Ditto that can learn transform, I really like the idea that Mew could be the ancestor of all Pokemon, or at least the Mew species. In how I’d handle it, Mew would be #1 in the Pokedex and would be the original Pokemon that could change shape at will. As the curious creatures as they are, mews explored endlessly, tackling any environmental challenges by changing shape into the various Pokemon species we’re familiar with to suit that environment. Over time, those mew who grew older and decide to settle in their areas in whatever shape they were in, over thousands of years, lost the ability to transform and remained in that shape as whatever new species they were. Because so few environments are comfortable for Mew’s natural form, and/or so few mew continued to travel endlessly, modern day mews are fairly rare, hence their legendary status. This would really help explain a lot of artificial Pokemon since the mew that originally became that species took on an artificial form for one reason or another somewhere down the line, rather than Pokemon like Klinklang, Electrode, and Klefki existing and being able to breed in some degree for no particular reason.