The first three generation members could sing & dance very well and, had their individuality that no one got overshadowed despite the presence of Kami 7, including their ace Acchan. Although it's revealed in Produce 48 that 48g idols don't receive any proper vocal or dance training as K-pop groups and they had to learn on their own from their seniors, IMO the early generation senbatsu members were at least trained to a certain extent, because at that time, there were only to a few members to be focused on. Back then, they even had solo singles and sub-units.