now it is mostly written for web browsers (between which there are no longer any significant differences in terms of standards compatibility).
At this point I think it is just a matter of time until Google (most likely due to their near monopoly with Chrome), will push for some new standard that they own and control and must be used everywhere. For some handwaving combination of security and protect the kids, etc. And google are in a great position to make it happen, don’t support it? Oh noes, your site is no longer listed in google searches.
And that will be the end of the open web, you can only use one browser that totally controls what you can and cannot do. Ad blocking is just the start, saving websites or images? Nah. We don’t allow that. Copy the url? No, you need to use this share button that has embedded tracking links in it, etc.