The level of accountability and, crucially, representativeness is much higher in the Dutch parliament though. The Netherlands has one of the most proportional PR systems in Europe, so it means that votes are highly meaningful. Yes, it means that really unpleasant people, such as Wilders's PVV party, regularly gain a high number of seats, but it is fair in the sense that it is an accurate representation of voter preferences. The UK, by contrast, is the only European country (unless you count Belarus) that uses First-Past-The-Post, which is the most unrepresentative electoral system that exists. This increases the disconnect between voter preference and the actual result, but neither Labour nor the Conservatives will ever reform it because they would lose out.
It is very hard to answer these questions here, as you rightly say, but I will give it a go. It is important to talk about presidentialisation/personalisation first. This phenomenon has been around for a long time now, but it has become increasingly dominant in terms of policy making and determining election success. Using Johnson as an example, he became the face of the Conservative party. He became 'the brand' that was used to break down the red wall and he was the factor that allowed the Conservatives to win in previously safe Labour seats. Think about how much Johnson was the centre of media coverage too and how all policy decisions were dominated by him and his inner circle. The marginalisation of cabinet and parliament in parliamentary systems is not new, but certain leaders exacerbate it. The UK parliamentary system is also highly susceptible to it due to the fact that most governments win elections with comfortable majorities and policy does not need to be a compromise through negotiation with opposition parties. If you consider the more consensus-based approach to policy making that is required in The Netherlands, the Nordic countries, and Germany, for example, you will see what I mean. This does not mean that presidentialistion does not occur in those countries, it does, but it is not so easy to achieve. Merkel managed it for years, but look at how much more difficult it is for Schultz by comparison. Rutte has also managed to be increasingly presidential in Blair-like fashion ('teflon Mark').
If you link all of the above to postmaterialism-materialism (the cleavage underpinning so much contemporary politics), voter volatility (which has increased across all European countries during the last ten or so years) and the declining salience of the traditional social cleavages (party identification, class, and religion), you begin to see why there is so much instability. The traditional cleavages clearly divided voters into left and right. The class (owner-worker) cleavage was a clear example of this. The working class voted for the left and the middle class and upper class for the right (N.B. some middle class groups voted for the left, but mostly it was the right). This has broken down as new cleavages with the postmaterialist-materialist division cut across the left-right axis, meaning that socioeconomic factors are less likely to be the determining factor explaining how people vote. Consider immigration, for example, which has been exploited by the populist radical right to gain a high number of votes. Immigration is not a left-right issue. As a result, these parties have taken votes from both the left and the right, which has left the main centre left and centre right parties struggling to respond. The old main parties do better when the agenda is on economic issues. The agenda is currently held by the populist radical right though and this is one reason why they are doing so well. This does not mean the economy is irrelevant though. Indeed, the the financial crisis and the poor response to it, especially from the centre-left, is another reason why disillusioned voters started looking for alternatives.
The response of many Conservative parties to changing cleavage salience and the rise of the populist radical right has been to move further to the right and adopt increasingly populist narratives (e.g. Johnson), but, and this is a very important point, the vast majority of populist radical right party leaders in Europe have moved increasingly to abandon previous policies that they held about leaving the EU (Le Pen, for example). Instead, they now advocate an illiberal democracy and a reformed EU in which the supranational institutions would be irrelevant and the member states would have all the power. You can see such alliances being formed by these parties in the European Parliament and by their leaders at European Council meetings. Le Pen, Meloni, and Orbán, have all spoken about the need to reform the EU and about pushing back against liberal democratic values.
The question that has particularly generated a lot of academic debate is what all of this means for democracy and specifically representative democracy. There is so much reading on this that it hard to point you in the direction of where to start. Simon Tormey's book from 2015 'The End of Representative Politics' might be of interest to you. There are so many books and journal articles about political parties and party systems that are of interest (Lipset and Rokkan's 1967 Frozen Party Thesis, Kirchheimer's 1966 'Catch All' Party Thesis, Katz and Mair's 1995 Cartel Party Thesis, and just about any of the recent books on anti-system parties/challenger parties by Hobolt and De Vries and Hopkin) that you could really immerse yourself in the topic. For high quality explanations of postmaterialism, new cleavages, and voter behaviour, I would recommend Inglehart (the creator of postmaterialism and the world values survey - there is a website dedicated to his work), Ignazi's 1992 journal article that is effectively a response to Inglehart's work not addressing the right, and Hooghe and Marks's 2018 journal article about the transnational cleavage.
On the issue of redistribution, I remain firmly of the view that there has to be redistribution to ensure fairness in society. The problem is that the entire global economy is structured to limit how much the state can provide support though and there is a very fine line between protectionism and ensuring that WTO rules are adhered to. The radical left's critique of the global economy, the free market, and neoliberalism is valid, but the problem is that they are unable to provide a solution or an alternative that is either clear or implemetable. Consequently, neoliberalism continues to dictate how the world works, even though the global financial crisis exposed its severe shortcomings and the inequalities that it has exacerbated. This is connected to the winners and losers of globalisation argument (postmaterialism-materialism), thus showing why the level of discontent is so hard for mainstream politicians to address.
One day, I dream that politicians will actually come out to say that the way in which the global economy works requires freedom of movement and migration. They never do though, as they are too scared to make the positive case. Until this matter is actually tackled though, I fear that there is little chance of ever being able to neutralise the threat from the populist radical right (or indeed some elements of the radical left). The extremes do not provide the answers. They serve only to fuel polarisation and dogmatic ideological discourse. The problem is that the mainstream parties have been left unable to find a convincing narrative and/or policy approach to satisfy a wide range of discontented voters, hence why you see the electorate becoming increasingly polarised across Europe into different blocs.