Here is my take, not that anyone gives a flying fart. I have not exactly been a huge Smith fan because I do think some of his tweets have been slightly past stupid. But, in regards to that guys opinion, maybe Brown and Marshall felt they were developed enough BECAUSE of Smith that they were ready for the league?
I put zero accountability on Smith for any offensive woes, unless I find out that he had any amount of actual responsibility for actually developing the pass attack.
My gut is, like most places, Smith is just a WR coach. Why does my gut feel that way? Look at his salary. He isn't get paid to develop the passing attack. Maybe he has a small amount of input, but I highly doubt it.
His job is to make sure the guys are learning subtleties, technique, etc. and develop relationships with the WR group and implement Urbans culture. Being a WR coach is not rocket science, and there is no doubt in my mind he understands what to look for in drills etc since he has learned himself from some very good receivers that have had success in the NFL.
I also do not agree with the "you have to recruit a kid that played WR in college and not an athlete". You can either catch a football or not. You can improve your catching ability, but if you can catch you can play receiver and if you can't you play DB. Every single one of these guys are fast. Every single one of these guys can make a cut. Every single one of these guys can make a fake. Obviously some are faster, shiftier, etc. but it is nothing magical about running a route. All of these guys have body control. All of these guys can be taught to go after and high point a ball. These guys are athletes. Most of them are very good basketball players too. There is no such thing as a "true WR" in my opinion. Look at Pryor. Look at Miller. Both QBs that are now playing WR in the most elite league in the world.