Lemmy is cheap compared to Mastodon though. You can probably fit a multi-user instance on the free tier of any hosting provider, provided you sweep media
You are on the biggest instance using software that passes your comment to every other instance that is federated with yours. I'm surprised it doesn't take longer than that most of the time.
To be fair, the federation happens in the background after the posting is done. So just posting alone only depends on the capabilities of the instance you're on.
Lemmy is decentralized, there is no singular Lemmy as a whole unless you're talking specifically about the server software. As a user you interact with your home instance, in your case lemmy.world.
Most connectivity problems and slowdowns are instance-specific unless you're talking about a federation problem specifically, for example you posted but it doesn't show up on other instances, that's a problem between your instance and the community's instance.
In your case you most likely just hit something on lemmy.world's side. Lemmy as a whole is way too small for them to even care about it.
I've been having sub second response times consistently on mine. This post submitted instantly.
Wow, you weren't lying about them "running a very old Lemmy version." For anyone else curious, on github, the newest version is 0.19.8, released 2024-12-13. lemmy.world is on 0.19.3 released 2024-01-22.
They tend to lag behind on purpose for stability reasons, but a year out of date is pushing it.
Part of the issue they have is that one of the most popular apps for lemmy, Sync, has been abandoned by its dev. They said they have roughly 5k/month sync users, and if they update, their experience will break further. The egregious part is that app has subscription options, and it's still been 10+ months since the last update.
I left Sync for summit a couple of months ago due to the above, and boy howdy is it better. Actual FOSS, huge amount of options, very similar ux and flow as sync. It's a champion.
Here's hoping more people trickle off of sync to a better app and lemmy world can drop that from their issues list.