Every coach is different, based on their own training, their competitive experiences, and the influence of the professional instructional training that they've had in the course of becoming an accredited coach. So it's quite possible that if you ask several coaches what is the second most important shot in squash, (behind the straight drive), you'll quite likely get different opinions.
So here I am giving my thoughts and explanation for which shot is number two on my list.
The second most valuable shot in a player's repertoire is the high cross court lob from the front corners.
There it is, and it is not an attacking shot: But primarily a defensive stroke. It's purpose is to get the player out of the deep front corners, with time to return to the central area (the T), and take up a ready position before the opponent has the opportunity to hit the ball.
It is good to note though, that a well hit cross court lob, that is high enough to go over the opponent, and drop down in the back opposite corner, often becomes an 'attacking' shot, as the ball's position in the corner will put the opponent under pressure. All while allowing the player to comfortably return to a controlling position on the T, or central area.
There are plenty of videos on YouTube, of various top players who effectively utilise the cross court lob. Immediately coming to mind are Peter Nicol, Rachel Grinham, and Nicol David.
But even players such as Thierry Lincou, and David Palmer, who both played powerful pressure games often use the cross court lob to counteract their opponent's attack into the front corners.
In fact, it would be hard to find any player in the top ten both women and men, who never hit the cross court lob. Some of course use it more than others, depending on the other shots they have in their repertoire and their particular speed and tactical approach to the game. Amr Shabana, Jonathon Power, and other world champions all have this shot in their bag.
In observing lower levels of the game, it is clear that many players either never hit the high lob, or they use it only rarely. As a coach, I suspect this is because when players do hit it, they often hit a weak lob, which the opponent easily intercepts and kills or drives away for a winner. Thus, players typically shy away from hitting it, and opt for either drops or hard flatter crosscourt shots.
The problem with hard cross courts is that whether they are high or low, they'll hit the side wall and then bounce out towards the middle of the court. This then requires the player to stay far off to the side while giving their opponent the whole front wall to hit to. So the result of the hard cross court, is that the player has not turned the tables, they are still under pressure, disadvantaged in the rally, with their opponent having three quarters of the court to attack into.
When watching juniors, and lower grade players this becomes very apparent. Even at the world level of juniors, the cross court lob is not used enough.
It's a matter of practice. Practice this shot, gain some consistency, get the ball high and slow. Then when you're in a match, and you've been attacked in a front corner, hit the lob, and if hit well, you'll immediately be released from the pressure, at least achieve equal footing in the rally, and quite often put extreme pressure on the opponent.