This is a very big point.
Without getting Scottish seats back, Labour is going to struggle because of the electoral boundaries elsewhere. Unless they are propped up by the SNP. And then you have to ask what would have to be given to the SNP to get that support.
However, Labour being a bit more near the centre might well get chunks of the midlands back at least. Bolsover being a non-labour seat is a total head-fry. First step is to re-build the red wall from here and heading north. Trying to win seats in somewhere like Buckinghamshire would be pointless. They weigh the Conservative vote to save time.
You say this, but it doesn't seem the case any more. The long-term trends in voting share (as in, over the last 10-15 years) have seen lots of the commuter towns around big cities - including in the home counties - becoming more and more yellow and/or red. Places like Guildford and High Wycombe, which are increasingly less populated by older social conservatives and more and more populated by liberal or left-wing younger families from the urban centres who have moved out to find more space. The inverse, in other words, of what's happened to so many northern towns in the ageing towns of the "red wall". Focusing on socially conservative retirees in the short term has won an election, but it's alarmed a lot of people who were brought into the party (either for the first time, or switching back from New Labour) during the Cameron years. It might not mean big Labour gains are coming, but on current trajectory places like Buckinghamshire look like new Lib Dem heartlands in the making.
2019 was a weird election, because while it was a terrible loss for Labour, it wasn't a landslide win for the Tories, and they still have a historically unpopular leader themselves. They have a healthy, but modest, majority, but they needed a massive popular vote lead to get it, and that was predicated on: 1) The most unpopular opposition leader as the alternative, and 2) The one-shot coalition-builder that was "Get Brexit Done" bringing plenty of people from across the spectrum who otherwise wouldn't have touched the Tories with a barge pole. I think without Scotland being in play for either Labour or Tories for the foreseeable, it makes it both easy to see how the Tories could lose their majority while winning the popular vote (again), and how Labour could well win the popular vote in the next election but struggle to ever get a working majority without some fundamental re-alignment similar to what we've seen in the red wall.
(For what it's worth, if I had to make a wild and probably inaccurate prediction now, I think that the big change over the next decade is rural seats coming into play. The south-west is mostly Tory now ofc, but it's been intriguing to see how, now that the Lib Dem hegemony there has been broken, a lot of those seats now look like Tory/Labour marginals rather than Tory/Lib Dem. Environmental policy is going to become incredibly important as climate change gets worse, and one thing Labour has put a lot of work into is how to reshape the economy in ways that are going to protect the landscape and environment... there's an opportunity there for a canny leader to actually try and make inroads among a lot of rural and agricultural communities, which are pretty much ignored completely in the national conversation except for when fox hunting's back in the news.)
