There's a few things in here I would say you're absolutely deriving from a fundamental misunderstanding of what they are.

• Gatekeeping: I'm not sure what this means in your context, but it sounds like you're imagining that some technically specific groups aren't fond of outsiders, and make it impossible for newcomers to join. What you may be misunderstanding is that some groups - just as in any other field - are specific to a catered crowd for a reason, while others or not. There are proper channels to go through to get accepted into said groups, most of which in the FOSS world would be to create something adjacent to that space that becomes popular and recognized. Johnny Newcomer wouldn't just be able to jump into the "1337 HaxX0rs Lounge" private IRC otherwise, but that isn't gatekeeping. I can't wander onto an MLB field, or an F1 racetrack just because I want to learn, and amateurs won't get access to similarly skilled people in the technical communities for the same reason. Teaching newcomers can be time consuming and takes a lot of effort, and people just want to focus on their own things in their free time.

• "Open Internet": The Internet by its nature is open. Access to it is not, because the hardware is not, and the delivery is not. As far as places people can't go, or don't have access to, that's quite subjective I suppose, but I'd say the majority of it is decided who is making what content, and how much they decide to charge for it and to where people can access it from, surely. If we dial things back 20 years, there was a lot more free stuff, but once corporations get involved - especially if they are publicly traded - they find ways to monetize everything. This does not prevent others from being able to publish at will whatever they want online, it just seems most people don't bother anymore. A "Closed Internet" would more suggest you had to "pay to play" in that sense, but I've never seen an example of that happening in the real world.

• Enshittification: I think you just missed the mark on this point from where the title and initial direction of your writing was heading. You're right about corporations making things shitty out there, but they can only affect their own little places on the Internet as a whole. People don't need search engines to use the Internet, they just prefer them. They don't need streaming services, they just tend to use them. They do need unrestricted access to human services (governmental or otherwise), information, and communications to really thrive in the world we live. The ones who are fucking that up are the corporations consolidating that physical access, and the authoritarian governments who are restricting how you get that access, and what you can see from it. This is what is leading to the massive partitioning and decentralizing of the Internet as a whole and it's services right now as we speak, which could be a good or bad thing depending on how you see it. Google censoring for governments is objectively awful, but there are other options.

I'm not trying to be nitpicky, so sorry if it comes off like that, but there's some big swings for ideas in your writeup that presuppose some of the smaller ideas above, that I think shape the very ideas you're writing about, but will unravel if thinking slightly differently about the root cause of them.