I think that independence would entail a great economic recession, seeing how companies relocated to other parts of Spain leading up to the (shitty and unserious) referendum. The EU said they wouldn't allow them to use the Euro if they got the independence IIRC. Even if they got it on favorable conditions, it wouldn't really make a substantial difference, they could be "bullied" by Spain as much as they are now, but with more symbolic sovereignty, maybe? Spain has the bigger companies and Catalonia would most likely be forced to trade with those, while critical industries like energy, telecomms and transport are private, so the ownership probably wouldn't be transferred.

I wouldn't take Catalonian independence too seriously, although I think some liberties should be granted. The concerning part is conservatives who are frothing at the mouth at the weakest independence effort, calling it "Spain's doom" or whatever tf, and at absolving some politicians who were initially accused of rebellion (as if they were armed) and finally charged with sedition, despite there not being much violence apart from some protests. They also disregard how ~50% voted for independentist parties on the elections leading to the referendum, wanting to sweep those people under the rug, as if that could be equated to solving the problem.

As someone who grew up in a exclusively Spanish-speaking region, I get how these reactionaries come to be. They think Catalonia/Euskadi/Galicia is just another region and "is Spain and therefore they must speak Spanish" (which the constitution says), completely unaware of those regions' history and context. I would dare say the majority of parents who want their children being taught in Spanish (something right wingers are very loud about, as all classes are given in Catalan/Euskera/Galician) are just (Spanish) immigrants. Most people there are born speaking their language and die speaking their language, just like the Spanish-speaking regions do with Spanish. Their languages were outright banned for centuries since 1715. No wonder lots of anarchists were Catalonian and Basque. Never mind the obvious asymmetry of having to learn a completely external language (external to the community, specially in reference to rural areas, which are the most pro-independence). Though I don't think this is a pressing issue, I still believe better policy should be implemented, either Switzerland's or Canada's way. Of course, there are other factors to the respective national identities, but to me it seems the most visible.

On the other hand, there's also that petty-bourgeois "we are paying for the rest of the country" line of thought. Again, the largest independentist party by far is right-wing. This may have been exacerbated by the economic crisis, austerity politics post-2008 and the general hostility coming from the right-wing government, but don't take my word for it.

I admit, I'm not an expert in the subject, so feel free to correct or dismiss me.