In 2017, the Conservatives gained 12 seats from the SNP. They lost seven of them back again in 2019, but by tiny margins. And they retained five, plus the one that they had already had, giving them more seats than the Scottish Liberal Democrats and the remnant Scottish Labour Party put together. The only constituency in Scotland with a Labour MP is the one with Morningside in it.
Therefore, the big winners from the collapse of the SNP would be, and at least initially will be, the Conservatives. They would also be the big losers from Scottish independence. This is not new. Mostly on sectarian grounds, Scotland was regarded as "a Tory heartland" until the 1960s, and the Conservatives controlled Glasgow City Council into the 1970s.
On 1950s Election Nights, Labour activists assumed that they had won, "But then the results came in from Scotland." Scotland provided Margaret Thatcher's majority exactly in 1979, whereas no Labour Government has ever depended on Scotland for its majority. In 1992 and in 2017, only Scotland recorded a net gain in Conservative seats, and in 2017 that was a very large net gain.
There are a lot of excellent arguments against Scottish independence. But "no Labour Governments ever" is not one of them, even if you particularly wanted a Labour Government. Nor is "everlasting Tory Government". I hate to break the news to you, but we have that, anyway. And the impending collapse of the SNP, welcome though that is in itself, will only consolidate that position, as much of Scotland reverted to its natural blue.