From what I've seen on reddit, this is sort of already happening. Lemmy's name isn't mud yet, but it's being spoken of like most of the alternatives over there: not good enough or flawed in some way. Lack of content and users is the main one that gets said about all of them, but beyond that, the negative things I see said about Lemmy most often are: "scatter-brained", "unintuitive", "tanky", "messy", "not respecting user privacy", "admins defederating and shadow banning", "having to apply to instances", "federated content not appearing the same on each instance", "lack of mod tools", "need a third party site to help find communities", etc.

And it should be said that many of the most common negative things I've seen said about Lemmy on Reddit are being addressed, but some are not. Privacy (public voting) and issues with admins erecting invisible walls in the federation through various means are not being seriously addressed as far as I've seen.

I think the main issue that will ultimately hurt Lemmy versus any other platform that comes along is that Lemmy's selling point of defederation is only a selling point to some people. Most people on Reddit don't care about centralization, they just want a platform like reddit. They'll come here and put up with it if they have too, but they will scamper off for a centralized site the moment one starts gaining traction unless Lemmy finds some way to provide something equally as unified, simple, and easy to use.

Maybe a frontend or app that just shows you everything and allows you to interact easily without worrying about logins or urls for instances, and pushes the federation aspect "behind the scenes".