I know that most people fall victim to confirmation bias, but I honestly don't see how people can't see the flaw in the OP.
ThreatMatrix covered most of it, but it bears repeating.
McElwain was at Fresno State for a single season. One. When McElwain arrived in Fresno returning starting QB Brandstater was a junior. Brandstater was drafted by the Denver Broncos in the 6th round.
McElwain was at Alabama for 4 seasons. In his second season at Alabama McElwain brought in A.J. McCarron. McCarron was good enough to grab the starting job and take the Tide to two national championships. McCarron became the first QB to ever win back to back BCS National Championships, broke the school record for TD passes in a season and passing yards in a season and became Alabama's all time passing yards leader.
At Colorado State McElwain inherited sophomore Garrett Grayson. In the three seasons Mac was at CSU Grayson threw for 8,648 yards with 62 TDs and 21 INTs. Grayson was drafted by the New Orleans Saints in the third round.
In his second year at Florida Mac signed the 5th ranked pro style QB.
Mac coached a QB that was drafted by the Broncos, a QB that won 2 NCs and was drafted by Cincinnati and a QB that was drafted by the Saints. Then he came to the Gators and there was zero depth at the QB position so he brought in the 5th ranked QB in the nation.
So everywhere Mac has gone he inherited a starting QB that has excelled in Mac's system and been drafted by the NFL and somehow that shows that Mac can't recruit. Except for that one time he did need a QB and he brought in a record breaker who won multiple NCs. However, the original premise states that you can only count the times when there was an established starter and you can't count the one time he needed a QB and hit a home run.
The original premise is that if you land a job that already has an established QB that is somehow proof that you can't recruit. The premise is so flawed it's laughable.
I understand those who doubt. There is no evidence that Mac can recruit his own QB. However, this is not evidence that he can't recruit QBs. The flaw in the original premise is simple to see.