He isn't perfect but he represents what could work about capitalism if there were proper safeguards. With him, he's governed by his own choices or morals, so the current system doesn't work because most rich people don't care. Gabe:
Provides a good base product
The product is based on being ran on open hardware that you own.
Uses his own money to advance support for a true open standard (Linux) because Windows is going down the toilet for UX.
Creates his own hardware that works with the product to give a walled garden experience if you want that. Or you can install your own operating system on the hardware, or install his operating system on other hardware, he doesn't care.
Doesn't have anticompetitive practices with people that make a similar product, focusing on being the best product.
Incorporates ease of use for other products into his product (PlayStation controllers, adding non steam games that are able to use most of the same features via Steam including Proton).
Treats employees well.
Is generous with the refund policy.
And guess what? Everyone is happy. He's happy and rich AF, his employees are happy, his customers are happy, his competition is happy because he's not purposefully throttling them (though they probably aren't happy he's eating their lunch because customers don't want them). The system can work for everyone if it is fair. We just need to demand these safeguards because even Gabe could change his mind at any time.