I'm think what you're feeling is not really the community duplication (although that's worse right now cause everything was dead 2w ago and there's almost no downside to making new communities cause almost nothing is well established), but rather the poor community discovery.

One of the engines that drove the "natural" aggregation of users in the big subreddits is that when you searched for subreddits the big ones were at the top of the list. When you search on Lemmy, the big communities may not be on the list at all. But I think folks recognize this as a challenge and will work on it. This week is about keeping the lights on though.