Nothing’s perfect, but there isn’t one main database to control. They can make the independent user harder to hear and to talk to others, but it’s far better than one domain where there’s absolute say on what can be seen and said. The main lemmy sites could go down and the rest would function, and others would grow to take their place. They’re only larger because they were active first and people weren’t aware they could pick others, or preferred to go where most were so it would be more active.