...granting the Tory party power over England and Wales until the end of time without having actually got their hands dirty by being seen to facilitate Scexit.
To reassure you, it's a trope that the Labour Party "needs" Scotland to win a majority. But it's useful for some to perpetuate it to hold on to Scotland. 
England gets the colour of government that it wants 
Look at the current Government: it won an 80 seat majority. 6 of which come from Scotland. Labour won just one seat in Scotland and the LibDems 4. Even if Labour had won every single Scottish seat, it still wouldn't have had a majority 
In 2015, Cameron won a majority despite only winning 1 seat in Scotland. Labour also only one seat (and the LibDems one). SNP won all the other seats. Even if Labour had won them, the Tories would still have won that election.
In 2010, Brown won 41 seats in Scotland and the Conservatives only 1. But the 11 seats that the LibDems won there helped Cameron form a coalition government. Even if Brown had swept Scotland, he still wouldn't have had a majority 
More to the point, Labour under Blair never "needed" Scotland to win his majorities - he had sufficiently large majorities without relying on the Scottish constituencies.
The only times Scotland has actually made a difference were in the 70s, allowing Labour to form a government (Wilson and Callaghan) and in 2017 when May was able to form a minority government thanks to the 13 Scottish Conservative MPs - although none of the governments were stable
Again, even if Corbyn had taken all the SNP and LibDem Scottish seats, he wouldn't have been in a position to form a Government. So we ended up with May and her confidence & supply agreement with the DUP 