This seems to me to be a clear example of an attempt to prevent a widespread opinion being discussed and measured. Those who don't want the idea to be expressed among themselves (i.e. within Catalonia) pulled out of the discussion in an attempt to discredit the mere discussion per se. Those who currently control the geographical area and oppose letting those who want to run their own affairs do so are trying to close down the idea's expression.
It is abundantly clear that a substantial percentage of the Catalan population wants at very least to establish what the percentages are for, against and undecided/uninterested. As others have said, the central government of Spain is looking the least impressive of the lot. The question is certainly not going to go away even though it is easy to imagine that today's referendum will turn out to be inconclusive, if only because of the disruption.
As also said already, this has nothing to do with the EU - in the event of Catalan independence, discussions on EU membership would follow, just as they would/will in the event of Scottish independence and in the case of any/all other European (and maybe even non-European) states which are (were) not already members.