The cameras that I've used which have been over 24MP, are where not only lens quality, but also shot discipline, support, and careful focusing/depth-of-field selection all become much more relevant and visible in the end results. Minor amounts of camera shake, focus error, or lens aberration that would be all but invisible on lower resolution cameras become hard to ignore as you approach 40MP.
Unless someone is looking to get into very large printing or pixel peeping for its' own sake, I would say stick to a 20-24MP full-frame or APS-C camera depending on system preference, with reasonable-sized good-performing modern lenses (no need to obsess over f/2.8 zooms or f/1.4 primes unless your obsession is amount of out-of-focus area).
I say this as an admitted pixel peeper and occasional large printer, who owns not one but two 45MP full-frame bodies, but am well aware of the inherent compromises and tradeoffs.
I was pretty pleased with the Fuji APS-C system as travel cameras when lugging my full-frame system wasn't reasonable. But ultimately I wanted those cleaner, finer detailed files, and once someone else could take the depreciation hit, I cobbled together a reasonably small FX mirrorless system. Admittedly it's not quite as small, light, or cheap as the Fuji system. But I was okay taking that hit for my preferences.