I agree with much of what you say there, Johnny J: it has been a subject of much heated debate, not just on music forums but in Scottish newspapers and there have even been song-writing competitions to write a new anthem for Scotland. It doesn't sound its best when bellowed by a raucous melee of legless supporters after a football/rugby match!
Incidentally, that video you posted shows Roy Williamson's original bouzouki, which sort of disappeared off the planet for many years, and has just recently been saved for the nation by a fundraising appeal: it is to be housed in future in Scotland's excellent museum collection of historic instruments at St Cecilia's Hall, just off the Cowgate in Edinburgh - well worth a visit if you are allowed into Scotland at present (and probably need to book an appointment! (Note St Cecilia is patron saint of music!)
See:
Roy Williamsons' Bouzouki