yeah i'm just tired of making the same argument over and over. for what it's worth i've been doing CSS "properly" since the time when that site was a thing.
back in the backbone days, now vue/react and before tailwind this is EXACTLY what we did, scope the styles down to the component, then layer it on top of the global styles. so sure, .my-selector a is specific to that component.
the "side effect" happens when your app starts to span 100s of components and you need slight variations for everything. you're telling me you can assure me that none of your master global classes contain any design definitions that could not possibly be reused? i'm calling bullshit. it's like saying your backend 100% never has any duplicated functions.
so with that out of the way, let's say you do get your global styles like 90% of the way there. so in each component you scoped it down. now lets say for one button you had to adjust the margin a bit, or another the styling is somewhat diff. multiply this by 100s of different components.
tell me now how me opening a file, seeing "button variation-class-1 variation-class-2", then going down into the component <style> section and looking up exactly what the variation and what properties were used is in anyway "better" than just seeing some super powered inline style directly in the button. it's the same complexity and now you've gotten rid of the prime benefit of CSS hierarchy and split the "style and structure" in just one independent component.
at some point you can't possibly create the number variations you need and you can't extract out "reusable" parts. maybe you have 5 buttons and only 2 need the 20px margin. do you create a "button 20px" class and do that in each component? no. at some point you will just inline it because it's easy, or you will create your utility class except it will be worse than tailwind.