In their current state, definitely not. There is a real bubble effect browsing on Lemmy because it feels like 1 post out of 3 is just praising the platform, but I think they’re far from ready to become mainstream. I’d say there are for now 2 major problems:
The global instability (a lot of bugs, many third party apps, but a poor on-boarding with the main website).
It was made by engineers and marketed by engineers. The federated aspect should IMO be public and known, but seamless. It should be possible to just create an account and start browsing without having to do some research on how the thing works. The technical aspect of the fediverse is great, but it’s also its main drawback, I believe that hiding it for newcomers could be a way of not scaring them.