The situation that "Government" in the UK finds itself is largely due to the insistence on retaining first-past-the-post.
No it isn't.
Since the 1830's governments of all stripes have managed to run the UK without the current chaos using essentially the same system.
Note that I am not defending FPTP, I am claiming the current chaos is not caused by it.
What has caused the current political chaos is a series of crises that each have led to culls of the most able people. It's the same dynamic as what happened to the Labour Party when they lost the 2010 general election. When they lost that, everybody associated with the loss and the "New Labour" government was tainted but the problem was that the people who were tainted were all the most able people in the party. The best person to take over the leadership from Gordon Brown would have been David Miliband. He was not chosen because of his association with the Blair and Brown governments. Ed Miliband's team was selected mainly from people who had avoided being tainted i.e. people were not able enough to take a significant role in Brown's government. Then, when Ed Miliband lost the next general election, and resigned, the process repeated. It's only now that Labour is getting back to a point where it has good politicians in key roles.
Now let's examine the Conservatives. The same process has been happening, starting with the Brexit vote. The government lost the Brexit vote and Cameron resigned. He and all the Remainers in his government were now tainted. That's a fair proportion of all the able politicians in the Tory Party at the time. The only way for a Remainer to get on in the Tory Party was to recant their own principles as May did and as Truss did. Since then there have been two more leadership changes and on each occasion, the people associated with the old leadership and often the opponents of the eventual winner were effectively culled. With Liz Truss we are now down to the dregs and it's no surprise they lack the ability to run a country.
This cycle is going to continue until somehow a general election is forced because the parliamentary party hasn't got anybody left who is both electable by the party as a whole and competent.