If you want to be more widely understood, it's better to sound more like the King of England than whatever your local variety is.
I tone down my (English language) accent when speaking to foreigners all the time. The point is to be understood.
I'm toning it down right now in this message. I want to be clear to a wider audience, not folksy.
So is Spain really telling other people the way they speak is "wrong", or is there simply a prestige accent, best utilised for international communication so the maximum amount of people can understand?
No, it has nothing to do with accent (phonetic). It's entirely language. They have a long history of "forbidding" words that are "real or not real spanish".
And by the way, counterintuitively, languages have NOT evolved to be better understood, but on the contrary, to "separate" or create cohesion in smaller groups.
"Spain" is not forbidding anything, the RAE [1] and the ASALE [2] are working together in keeping a common tongue. Don't allow some chauvinistic view to cloud your judgement.
There are royal academies in each Spanish speaking country. Is a very old institution that creates diplomatic links and a help net between countries on everything related with the Spanish dictionary. They solve doubts for free, or publish American Vocabulary dictionaries (so American people can understand other American people).
If you want to understand Spanish this is the best resource available
Not all people in this academy descend from the Borbons. Not all people there are from Spain. All are voted by their peers based in their perceived merits. Is a meritocracy, not a monarchy.
Some people appreciate the fact that there are experts on Spanish language trying to help everybody. Other will keep saying the equivalent to "Experts thing that are better than me" or "Death to conquerors. Mine is better, Murica!!". Everybody has their own choice, but the reward is ending with a language that nobody will understand. A very silly prize.
They have a long history of being proscriptive for anything that isn't "their real spanish" (that being of Spain). In latin america, we use a lot of neologisms ("commitear", "pushear", "mergear") and those are strictly "prohibited" by them, to the point that some spanish universities, following RAEs recommendations, fail students using them.
Any centralized institution that is in charge of overseeing a large and diverse number of countries that have evolved spanish over the past ~400 years is, in my eyes, set to fail.
Now, I do use RAE all the time to check definitions, but I see it as a "descriptive" body, in charge of creating some definitions. But even some of those definitions have to be "scrutinized" and can't be literally and blindly trusted. For example, check the definition of "gitano", which has a clear pejorative connotation. That is not wrong, is just the reality of how the "spanish speaking world" expresses itself. But should you take that definition by heart? I don't think so.
This is a clear example of "The Cathedral vs the Bazaar", as in Open Source vs privative software. I'm a hacker, I prefer a bazaar to a single institution dictating how we should talk..
You know that the RAE [1] work together with the Asociacion de Academias de la Lengua Española (ASALE) [2], right? You are showing the RAE in bad light, while both the RAE and the ASALE work together when creating new editions of the dictionary or new grammar rules.
About your "neologisms", no they are calcos or loan translations [3], they are not neologisms. They would be neologisms if they were new words, not copy of words from other languages.
