I think it's because people see capitalism as one thing, while in reality they are implemented very differently.
The nordics are not successful only on their capitalism. It's because it is regulated, and because the money is distributed more fair than in other countries.
The Nordic countries are also on Earth, which we are destroying. Some of their wealth comes directly from that destruction. Norway is the 5th and 3rd largest oil and natural gas exporter, respectively, making their happiness the result of good social policy that makes up for capitalist inequality which is directly funded by destroying the Earth and fueling capitalism elsewhere.
Even setting the climate aside (a ridiculous thing to do, really), the Nordic model isn't possible to sustainably replicate elsewhere on Earth on capitalism's own term, because we can't make every country a net exporter of the most desired commodities for obvious reasons, or the beneficiary of complex historical circumstances, like neutrality during ww2 (Sweden), or a long-time colonial power (Denmark).
Put another way, there is no Nordic model available for Bangladesh, whose workers work six days a week in factories to make the cheap clothing that happy Norwegians wear. Norways needs Bangladeshes to keep their standard of living.
In a previous job, I spent a good amount of time in a Bangladeshi garment factory. That specific factory in which I worked had been on strike a few years prior, requesting a raise to dozens of dollars per month. That's not a typo -- per month!. The police fired into their picket line, killing and wounding hundreds. This fall, Bangladeshi garment workers went on strike again, demanding a tripling of the minimum wage from its current ~75USD per month.
The urban poverty that makes my life possible, so far away, out of sight and out of mind, is an absolute fucking disgrace. We should talk about it daily. When they go on strike, as those garment workers are now, every single westerner ought to strike in solidarity, even if motivated by nothing but shame. Instead, we don't even know that it's happening, at least in the anglosphere.
I've since become convinced that there''s only one path to a just and verdant world -- international solidarity. Communists and anarchists have filled libraries with ideas for what that might look like. I've read some tiny sliver of that corpus. If you actually want to know why some of us want capitalism defeated (beyond the anecdote that I just relayed), or if you're curious how much better some of us think the world could be, I'd be happy to point you towards books that spoke to me.
Going to give a wide range of answers based on topic, so you can pick up what interests you. Happy to give more if none of these appeal to you.
If you work in tech, Stafford Beer's Designing Freedom. It's very short, accessible, and full of so many big ideas about what computers are for that it exposes the tech industry's absolute fucking poverty of vision.
If you're interested in deep dives on more technical topics, David Graeber's Debt. It's a fucking tome, but it's also amazing. So much of what we take for granted in our world is completely arbitrary and made up, but no less powerful, and there's nothing quite as arbitrary and powerful as the concept of debt.
If reading a cinder block based on an internet stranger's recommendation is too much for you, maybe try Graeber's Fragments of an Anarchist Anthropology, or his The Utopia of Rules instead, depending on which topic interests you more. Graeber is a great place to start because he's accessible but also his mind isn't limited by the confines of capitalist realism in a very special way. He was truly one of our best.
If you want something that's extremely light and fiction, I recommend William Morris's News from Nowhere. It's extremely cringe in a way that only 100-year-old socialist utopian fiction could be. It's excessively sincere, even naive, in a way that rings hollow to our cynical modern selves, but it's such a short read, and it's so adorable. I like the way that he challenges the concept of work. I think that the modern left should revive that line of criticism. I also enjoyed that you can see early versions of things that we associate with more modern movements in his utopian vision, especially degrowth and reforestation/environmentalism, not just for "the environment," but with nature as a part of and inseparable from the human experience.
Finally, if you like philosophy, and you want in depth analyses of capitalism, and don't mind something that's maybe less accessible, I recommend Adorno and Horkheimer's essay The Culture Industry. It was written in the 1940s, and it reads prescient today. They saw the rise of capitalist mass media as more than just a threat to independent thought, but a pacifying, homogenizing, almost all-consuming force. If you want something longer than The Culture Industry, and probably slightly less accessible, I recommend their Frankfurt School colleague Herbert Marcuse's One Dimensional Man. He basically argues that capitalism, and more specifically what he calls "technical rationality," has conquered our culture and our very ability to reason, at scales big and small.