There are far less than 255 countries in the world, and most countries do not have 255 regions.
On the other hand, most regions have more than 255 subnets, and with NAT these days, most subnets have faaaaar more than 255 devices
Why would a main server be required if users can fluently interact across Instances? (which, imo, is an area where lemmy has the most margin for improvements)
I don't think a "main" instance is something we want. If one instance completely takes over the whole federation, we will have another reddit debacle in a few years.
While Decentralization is not a silver bullet against monopoly (just look at what gmail did to e-mails), centralization seems to always kill independence once platforms reach a critical mass
I think with the influx from reddit, which gathers a lot of technical users (which I think are also among the first users to migrate), I can see lemmy getting a lot more contributors in the coming days/weeks.
Among the features I'd love to see happen, some would also address your concerns about the lack of centralization :
While it's very similar to botw, it fixes a few things and introduces a lot of new fun mechanics. If you enjoyed botw, there is no way you don't have fun with totk.
The last two Zelda games (especially totk) lets the player get really creative as well
Reminds me of the time used a private gitlab repo for a freelance contract where I was working alone. I used it to keep track of tasks in issues. Some issues in this repo really turned into me talking to myself