KDE is heavy, but that's the magic of Linux. It's to you to figure out your perfect combination.
I'd argue that if you don't care how computers work, buy a Mac. If you actually enjoy the process Linux is great.
In terms of install size, performance is usually higher than on lightweight DEs.
Linux on Desktop is especially great for used Laptops. In that case the Linux community had a bit of time to adjust to the hardware.
Laptop also offer a well defined hardware environment where you know exactly what's inside.
Once you additional devices the range of hardware that needs to be supported is so much wider and so is the risk that something does not work.
However, especially for more casual users to just use your Laptop and not connect anything ever is in my opinion a quite common use case. There you can optimise to support some Laptops really well. And that is where Linux can shine.
They are overpriced for 2025 (especially because the height-adjustable stand costs quite a bit extra). But they wake very fast from sleep and work fantastically with a Mac.