I think it’s a lot more complicated than what you make of it.
If you’re designing with just one set of system specs in mind, you can easily end up with either a laggy-as-hell-on-less-than-ideal systems (see: Cyberpunk 2077 and how it ran smooth as butter on systems with SSDs and the latest PC/console hardware but looked like abolute dogsh** on systems that aren’t the latest-and-greatest, which is made worse by the ongoing chip/GPU shortage), or you can end up with crappy-looking-on-better-than-minimum systems (see: how upscaling can look horrible if you don’t have DLSS 2.0… and even with it, there’s a limit to how good that technology can make games look like).
While video games have gone a long way — enough to make going the way of mobile phone graphics (e.g. Warcraft 3’s latest “update”) questionable to laughable to rage-inducing — that doesn’t mean that we should look at low end PCs with contempt as if good game design was defined by graphics and compute power required. Undertale was an 8-bit game that earned many nominations and awards despite looking like it could work on a toaster. Doom is an old PC game that still garners attention even if it could literally run on a toaster. And you’ve got so many innovative games (some can be seen on itch.io) as well as well-designed and entertaining games that can and do work on low-end PCs, alongside cross-platform games like GenshinImpact who can look amazing even on phones, let alone PCs.
I would assert that low end PCs improve game design, because for you to have your game run on low end PCs despite the lower specs, that means you need to optimize your code, use methods that make the game run more smoothly, and allow you to determine how important some elements are over others in conveying your game’s story and aesthetics. So when you have that game run on a high end PC, not only are you able to have your entire game run way more smoothly thanks to the game being better optimized, you can add to enhance the experience rather than subtract to make compromises.