Ultimomono, its always a pleasure to read you. I learn a lot about my own mother language with your posts, thanks. Let me explain a personal opinion on this matters. First say that I'm far from being a linguist, just personal interest, thus i'm an ignorant compared to you in these matters.

I'm from Balearic islands, raised bilingual spanish-catalan. Here there isn't a truly cultural historic dialect of spanish. We just try to speak like castilians do. Like you say, everyone here thinks that Valladolid, or whole Castilla is where good standard spanish is spoken and that's what we should try to speak. But, as you say, is just another one more dialect. I understand that the pure standard spanish is an idealization only possible in written language. Ok, but the dialect spoken in Valladolid may be the most similar to a theoretical perfect fonetic use of the standard written language. It's written as it's spoken. I think that's why people like it this way. On the other side, my experience with catalan is quite different. We have our cultural inherited own way to speak it, in fact every island has its own way. We would never try to speak like a Catalan from Barcelona (closest to standard/written catalan) like we do try to standarize our spanish (speak like castilians). Most of us think that standard catalan sounds bad, artificial and spanish influenced version of what we speak, and something you only use when you write. The difference between both impressions? I guess it's the cultural heritage. Our true mother language is our catalan dialect, not spanish, not standard catalan. We use an external dialect of catalan as an standard when we have our own way to speak it. I think we don't like it beacause there is little correlation between how we speak it and how we should write it. Just wanted to point out how opinions in the same society can change depending on your own cultural filter/heritage. We like and try to speak "standard Valladolid spanish" but we don't like to use "standard Barcelona catalan". And i mean literally "like", while we may not like some of its lexic and grammar, many still love to use it in official, high cultural situation, etc... instead of spanish. I'm not speaking about diglossia, it's more of an aesthetic experience. Here we also make the distinction between y and ll, also between b and v. I know it's a catalan influence but i will never in my life pronounce "vaca" and "baca" the same way... v upper teeth + bottom lip, b both lips. Even if i know that this is not correct in spanish, for me has a better correlation with what i read, thus making it easier to read/write. Overall, I guess all this problems comes from the faster evolution of spoken language versus written language... Thanks again, and hope you found of interest this particular case. Saludos!