You really answered your own question - why are people so down on Milroe? it's because he hasn't yet shown several things he should be able to do to be an effective QB. The same was true of Hurts - it was very true that he was pretty much a one read and run QB for his first two years. Milroe shows that same tendency right now, but Milroe, right now, is not even close to where Hurts was, as a true freshmen, as far as timing, anticipation, and honestly just passing consistency.
What happened was Hurts got benched for someone who'd make all the reads and make sure the WRs were all involved. In year three for Hurts, once Tua got the start, he started forcing himself to progress in making all the reads and be more patient - he had to or he would not play anything more than mop-up. Sometimes a hard situation like losing a starting spot is a great way to get motivated to get better in certain areas and Hurts certainly did that - something that should earn him a lot of respect because not everyone has the type of character to react the right way like he did. We are now at the beginning of year three for Milroe, and really we are not seeing much at all yet.
I think we all want to give him a bit of grace cause I don't know that he got great QB coaching his first two years, but really we'd expect more from a 3rd year guy than we are seeing now. that said, I'll be just as happy for him if he turns the corner and starts progressing in his developmental areas as I was happy for Hurts when it became obvious he was making significant strides.