The SNP's record so far has indeed been disastrous - for the Scottish Labour Party and generally those who are spiritually wedded to the status quo.
For those who are willing to think afresh, independence holds the possibility of doing better than the UK, perhaps as well as other European countries of similar population size, maybe even as well as, for example, little Iceland which fairly consistently outdoes the UK on the social and economic measures that really matter, often by an enormous margin. The other countries are only outdone by the UK where the criterion is sheer size (grand total - not per capita statistics, quality of life, etc.), surprise surprise. Of course, facing backward toward past battles, wars, conquests and empire (historical nostalgia and perceived superiority) would be replaced by facing forward (reality, no more illusions or "heroic" adventures). It might be contagious and also wake up and thus benefit the remaining UK - I suspect Scotland and the world would welcome that.
Oh, the comparison countries do not significantly, if at all, benefit from oil or gas (Norway thus excluded) - Scotland has just as good assets in other respects, established activities/earners and not least its people - oil was always stated as a bonus not to be squandered (on propping up failing governance). Saying that Scotland could not survive outside the UK was the nonsense and insult that raised the Yes total from the predicted 12-20% initially (cocky UK establishment) to 45% at the end (incontinence pads de-rigueur) after frankly pathetic spectacles with much of ex and current Westminster making fools of themselves (but admittedly swaying those afraid of change, and there are many of those) - make no mistake, the referendum was an enormous SNP success.