The issues with SP's keys are minor IMO. Doubleshot legends are clean and precise in a way that dyesubs just can't match. And the color options are much greater. For legended keys, I much prefer 2-shots, whether they are from Cherry or SP. For blanks, which I also really like, PBT is my preference.
i'm agnostic on 2-shots vs dyesub. all known PBT molds (including SP's) have a satisfying *thunk* that ABS can't quite match. OTOH 2-shots are sharp, contrasty and have huge color varieties that PBT dyesub can't match.
anyway, the point is that the different materials and processes have different engineering tradeoffs, and SP's 2-shot process hits a really nice point on the tradeoff curve for the vast vast majority of people. there are a few people who don't care for them but it's literally a few people.
as for KBC's PBT caps (the chinese PBTs you're referring to), those hit a different point in the tradeoff curve. the color variety is significantly smaller, but they have the do have the PBT thunk and can be dyesubbed with legends of arbitrary complexity (but not color!).
personally, my favorite thing to do (as you'll see with the geekhack pack) is to mix and match the two according to one's needs regarding style, profile etc. in particular, KBC caps can be obtained in cherry profile, which is very very close to the SP profile we use, EXCEPT that the bottom row is flatter. some people (notably tsangan, god of keycap collecting) swap out their SP spacebars with KBC cherry spacebars specifically for specifically this reason.
anyway, the point is that all the manufacturers we work with make high quality products, but there are a lot of tradeoffs involved in making keycaps. we work with the firms and people we do because they're all very good at hitting different points on the tradeoff curve, so it's a gross mischaracterization to say that no one likes any particular keycap model. of course, people have their favorites, but for the most part people enjoy having a variety of parts to choose from, just like with keyswitches.