A major downside of FPTP for a long time in General Elections is parts of the UK not getting governments that have been voted for. For example, this what I had posted in one of the Brexit threads a long time ago explains the major flaw with FPTP General Elections since 1979 with the following voting patterns and results for Scotland (and similar to my original neck of the woods of the West Midlands, minus SNP as they don't stand candidates outwith Scotland):
1979 - Mainly Labour, got Conservatives
1983 - Mainly Labour, got Conservatives
1987 - Mainly Labour, got Conservatives
1992 - Mainly Labour, got Conservatives (only just, due to a late swing in the day to the Conservatives)
1997 - Mainly Labour, got New Labour (which were not new, and were most certainly not Labour)
2001 - Mainly Labour, got New Labour (which were not new, and were most certainly not Labour)
2005 - Mainly Labour, got New Labour (which were not new, and were most certainly not Labour)
2010 - Mainly Labour (with the only constituency changing hands was my former one of Glasgow North East from Speaker to Labour), got Conservative-Lib Dem coalition
2015 - Overwhelmingly SNP (with 56 out of the 59 constituencies, with the remaining 3 being 1 each to Labour, Conservative, and Lib Dem), got Conservatives (only just, due to errors in the polling methods)
2017 - Mainly SNP (reduced to 41 constituencies), got Conservatives with some support from DUP
2019 - Mainly SNP (increased to 48 constituencies, including the unseating of the Lib Dem leader at the time Jo Swinson. Her lips moved with every lie she told which explains how Swinson lost her seat), got Conservatives
No matter what the voting pattern of Scotland is at General Elections, since 1979, Scotland has not had the government it has voted for. Although I do understand the reasons how Scottish nationalism has become fashionable nowadays, I do not support the SNP's version of independence. I would like to see the whole of Great Britain (assuming Northern Ireland is returned back to the Irish) having progressive federalism, but this topic would be better in a different thread rather than here.
With proportional representation, at least the results would closely reflect the voting patterns, and regions would actually get the government that has been voted for.