Judges can only act within the law, and as stated previously; folk think the laws are too weak.
That said, some of the sentences handed out do appear lenient, even when the guidelines are being followed.
You don't need legal expertise to observe and form an opinion, though clearly it helps to consider all aspects in reaching one.
Strangely, on many many aspects of society, folk tend not to consider the big picture, and politicians utilise that.
Those same politicians who will introduce legislation that judges and lawyers have to follow.