"In the end people will have to learn that it isn't just 'padlock or no padlock' but that they need some indication of certificate quality. We could certainly do with speeding up DNSSEC for example. But I don't think Lets Encrypt really weakens TLS --- rather it makes people aware of the weaknesses inherent within it (and any digital certificate scheme)."
But what if the Average Joe is just plain too apathetic to care? IOW, what if the minimum necessary level of security is just too much hoop-jumping for them: basically a bridge too far? Like settling for dead bolts and not caring about cinder blocks through windows?