I will grant you that a high proportion of illegal aliens and felons can skew the result. However, I would have to see what the ineligible felon rate has been throughout the period mentioned, 1932-present. You can claim it's more now, but I'd want some sources and numbers. Voter turnout vs registered voters is only one piece of this discussion, about whether making it incredibly easy to register and vote has increased voter turnout. The rate of registration among eligible voters has to be considered. If someone doesn't bother to register, despite the ease with which they can do so compared to 30 or 50 years ago, then all the handholding hasn't helped.  Registering can't be the goal, voting is. 2016 was a 20 year low in turnout of eligible CITIZENS (which removes the illegal and resident aliens)
 http://www.cnn.com/2016/11/11/politics/popular-vote-turnout-2016/index.html