The problem is who decides when an instance contains “nothing of value”? You’re leaving that up to a small handful of admins. You could also encounter a situation where multiple admins collectively decide to defederate from anyone who doesn’t subscribe to the same block list, so any instances who hold different opinions are cut off from loads of content on other instances. We run the risk of splitting the fediverse up into multiple, totally isolated chunks which I don’t think is a good thing on the whole.
For your first printer I would recommend getting something you can build from scratch if you have the time. You’ll learn about all the different parts of a printer so you have an idea of what to do when something goes wrong. Prusas are great in that aspect as they have wonderful documentation and assembly instructions and it’s easy to buy replacement parts if you need it, plus they’re pretty low-maintenance once built. In your price range I think the MK4 kit would be a good option, just keep in mind that assembly can take upwards of 10 hours depending on how fast you go.
However, if you want to buy something and just forget about it, one of Bambu Lab printers would probably be a better option. Their parts are more proprietary and you won’t get the same learning experience, but its dead simple to setup and use. (Not to mention incredibly fast).
Either way, you’ll be getting a solid printer that should last you for a while, so have fun and be sure to post here if you have any more questions!