Coalescing into massive communities is a mixed bag. Putting all your eggs in one basket makes them more vulnerable to rogue moderators, sudden loss of a server, the need to defederate if the host server gets compromised, provides a more attractive target for bots, and other bad actor things.
Yes it would improve ease of use and make Lemmy more newbie friendly, and it can be frustrating to have conversation splintered. Lots of times I’ll comment on an empty story at the top of my new feed only to find a lively discussion a little lower. That’s all frustrating, I agree. It’s also, I think, the nature of federating.
If multiple different news communities are thriving despite posting pretty much the same content, there are reasons for that. People can pick just one to subscribe to, and they don’t all pick the same one. That tells me there is something about each one that makes them attractive to different people.
I think it can really hurt smaller communities, though.