Britain is a unitary state, not a federal union. 1 man, 1 vote as citizens of the United Kingdom. Britain voted to leave. If the arguments for staying in the EU are based on trade and a single market, Scottish independence is nonsensical, as Scotland does over 60% of its ‘external’ trade with the rUK. The entire economic basis of Scottish independence was based on the assumption that the rUK would stay within the single market and customs union. Once we GTFO of that, the case for Scottish independence has collapsed. :D
you are correct, Britain is a unitary state where the Scots have far less ability to influence matters of importance to them, in the British union than Ireland has in the European Union.
And you are also correct that right now there is no economic basis for Scotland leaving the UK and into the EU. I don’t think this means that the “case” for Scottish independence has collapsed, any more than the removal of proof for England economics outside the EU has made leave support collapse. But the economic case is not there, yes