You're not really addressing GP's point, IMO. The tech isn't really the hard part about Instagram. The market penetration and now monetization is. No one is going to use pixelfed over Instagram because the whole point of using Instagram is for the network effects (clout). If people move/continue to move off Instagram, it will be for something that more effectively connects them to fame and reach, like TikTok.
No, it's not complicated stuff to build something like TikTok and Instagram. But it is complicated to do all the other important parts besides building it, which are just as important if not much more so. To get people to use it, and to incrementally improve it 0.1% more week over week -- that's the part that you need a full company to do, and that's the thing that a lone founder will struggle to do.
This is undoubtedly true. My point is, if you don't build, you can't do any of what you are laying out. My point isn't that you should recreate Instagram, but that these kind of apps and apps like it are not difficult. Virality is worth more than you think, and figuring out how to make 80k a year is much easier than trying to make a unicorn.
It took Twitter 10 years to increase the message size. It's not hard to incrementally do that as a single founder, you can probably make changes like it in a single night, and you can probably do that with a lot more ease than if yo've got a team and expectations.
I'll take the counterparty to your claim. My counterpoint is that you don't need to build to do any of what I'm laying out. You can validate the market for what you're trying to do with content, lead generation forms and spreadsheets. My point is that it _doesn't matter what_ you build if you don't perceive the right customer need and react to it appropriately. At least for me, it's very easy to focus more on building something (because it's fun) than it is to go back to the drawing board if an idea isn't good enough (because that's psychologically exhausting).
No, it's not complicated stuff to build something like TikTok and Instagram. But it is complicated to do all the other important parts besides building it, which are just as important if not much more so. To get people to use it, and to incrementally improve it 0.1% more week over week -- that's the part that you need a full company to do, and that's the thing that a lone founder will struggle to do.