The semi-decentralised nature is part of the point of the service, you can join a small, local server and still subscribe to communities on larger instances and it (in theory) all syncs up and works.

multiple servers spreads the load, heck, you can host your own lemmy instance on your own hardware and still seamlessly communicate with large ones like lemmy.world once it synchronises.

Downside (apart from the inevitable shutdown of smaller servers without admins willing to put the time and money in leading to lost accounts) is that communities aren't automatically fetched, so sometimes you need to paste the url into your instances search bar to get it to sync to your sever, then you can subscribe. I picked a medium size server on the other side of the world because I had no friggin idea what I was doing but now my feed is full of content from all of the big servers.

I think the slow and steady development from the last few years will now speed up a lot as more and more people use the service and find new limitations, new features, fixes and optimisations will come.

So far, it's handled the massive influx of users very well.