The last Republican president won fewer votes than his opponent and was still elected, and the one before him (GW Bush) also lost the popular vote the first time around. Biden won the 2020 election by about 7 million votes (about 4.5%) but if Trump had won about 100,000 more votes distributed in the right places, he could have won. Yes it turned out fine in 2020, but it's hardly a foolproof system when it comes to kicking out an unpopular president - or ensuring one doesn't get elected in the first place.
Unlike in the US it's not possible in practice for a party that isn't the largest to win a parliamentary majority in the UK (though it would be in theory), but I wouldn't describe it as especially fair - you can get a healthy parliamentary majority with about a third of the overall vote, as Labour did in 2005. That isn't fair in my eyes. Whatever other problems there might be with PR, at least it's more democratic.