Well, you know wrong and your 'arguments' don't make any sense. Every country has a region that's an 'economic powerhouse'. Do you believe each of those regions should become independent? You know why Catalonia is an economic powerhouse? Same reason as regions in other countries:
- geography: this region is simply conveniently located to build industry there, has proper resources and good climate
- politics: Spanish government purposefully moved a lot of industry from other regions to Catalonia. They didn't simply build it, it was uprooted from other regions and moved there
- migration: a lot of hardworking people migrated there after industry was moved and worked to build strong companies there
- strong internal market: Catalonia is selling it's products to Spain. Without a strong market in the rest of Spain they would not be able build their economy. Until Spain joined EU they would face tariffs and would have difficulties exporting.
- investment: central government invested a lot of money to build roads, railways, port and airports in Catalonia.
Obviously there are other regions that could be an 'economic powerhouses' of Spain. Without Catalonia Spain would simply invest in other regions and consolidated industry there. The idea that Catalonia grew in a vacuum and built it's economy independently from Spain to later be invaded and exploited is simply a lie. It's a integral region of Spain that have seen a lot of investment. Investment made by Spain with the cost of big national debt that Catalonia want's to avoid paying now. That's what it comes down to: Catalonia want's to take the money and run away.
Now to you 'cultural and ethnological' reasons. Historically (until 1990') only bout 20% of Catalans considered themselves different country and wanted independence. That's because till 1990' the independence movement was based on cultural and ethnological values. It didn't really worked, 80% of Catalans still felt they are Spanish. In 1990 Catalan leaders started talking about money. Their arguments shifted to "we are the economic powerhouse, we should keep all our money" (sounds familiar?). Suddenly support for independence grew to around 50%. It's not because their culture changed, it's because people there understood that disrupting Spanish politics and fighting for independence will give them money. That's what it's all about. This rhetoric also ignores the fact that 50% of Catalans still consider themselves Spanish citizens and want to live in Spain. They are being actively discriminated by Catalan government and in case Catalonia becomes independent will entirely lose protection given them by Spain. Supporting Catalan independence gives Catalan green light to discriminated half of their population. Keep that in mind next time you will promote Catalan propaganda.