Do they sometimes initiate an exchange, after you've taken the original initiative?Even if not via questions, per se, there must be some indication that your interest is returned.
If not that, if they don't have the brain to carry a decent conversation, that's a turn off in itself and I still delete their emails.
First off let me just salute you for boldy making the first move and distinguishing yourself from the notion that all women want to be chased and HAVE to be approached/ messaged first.
This factoid, coupled with the fact you have an advanced degree, is going to create a modest amount of frustration.
Given that we're on a free dating website you're going to encounter everything from ditch-diggers, to surgeons, to everything that is in-between.
Plentyoffish dating forums are a place to meet singles and get dating advice or share dating experiences etc.