Love all the amateur psychology going on here, maybe we should just accept we are not that great.
The main problem in my view is simply as always finance, if the SFA and the government had thrown a decent amount of funding into the game years ago we would not be so hamstrung. (also, monies spent have probably gone to the wrong places probably as they are overseen by knob-ends)
Although I do agree the Scots culturally have a tendency to self-destruct the main reason I see not only in football but other major sports in Scotland is lack of funding.
In the days gone by, Scotland would get knocked out not because of a lack of talent but due to self destruction, now however, in my opinion its because of zero funding culminating in a lack of talent and general self destruction culminating in utter disaster at all levels of the game.
I'd also like to add I live in Australia and although it has a bigger population they seem to excel at most sports they take part in some of which aren't there national games.