That's not really a fair comparison. Losman is only in his third year, Plummer his 10th.
For those that think JP is bad, at the same stage of his career, Jake Plummer was absolutely awful. The numbers pretty much tell the story:
1st year: 53.0%, 7.4ypa, 15 TD, 15 INT
2nd year: 59.2%, 6.8ypa, 17 TD, 20 INT
3rd year: 52.8%, 5.5ypa, 9 TD, 24 INT
4th year: 56.8%, 6.2ypa, 13 TD, 21 INT
That's about as bad as it gets statistically. The worst was clearly his third season, when he nearly threw three times as many INTs as TDs. Losman hasn't even approached that level of futility.