Valve is also not publicly traded and they have a succession plan of some sort in the event that gaben kicks it, I can only assume whatever he's come up with is sound, he's done a great job of running the place so far.
To play games i use UMU Launcher which is basically Proton minus Steam (or Wine plus DXVK, etc, depending on how you look it at). I use the "raw" UMU Launcher with its own command-line utility, though it can be used as part of Lutris for a GUI-based experience.
Steam's near-monopoly was earned by simply being the best store. Other stores like Epic don't even include basic features like a shopping cart to buy multiple games at once.
I could go on and on about why Steam is so much better than any other store, but this isn't the place.
That said, I can understand being nervous. Steam is great because it's privately owned and GabeN is happy with the money he makes from it and doesn't feel the need to enshittify it in order to get more money. But eventually he will die or retire, and someone else will be given control. Supposedly, he's already vetted some people to take the job, but what's to say they weren't merely playing the part and will take it public as soon as they can?