Babe Ruth and Walter Johnson were elected the first time there was voting, and so they were up against everyone who had ever played to that point. But it is hard to understand why some people didn't vote for the likes of Willie Mays, Hank Aaron, Ted Williams, etc.
I would say that the BBWAA have done a very good job (putting aside the strong opinions on both sides for the PED guys). A few marginal guys have gotten in, but if several hundred mostly knowledgeable people voted them in, I have no problem. I agree that it has gotten better; I think some of the old timers had personal biases for and against certain candidates.