Show don't tell are the words of writing wisdom

It's been a long time since I blogged on this site. The fact is I have been involved in a labour intensive house and garden renovation that has left me pretty much no time for writing, editing or book marketing. As a consequence book sales have dwindled and my attempts to land a literary agent or a mainstream publishing deal have run aground.
I did have a brief involvement with one major agent who really liked 'The Immortality Plot' (the book I have been concentrating on for some time). He used words such as 'gifted' to describe my writing which did my ego no end of good. 
There is always a but somewhere. He felt the book needed work. In particular, he said I should streamline it by reducing the involvement of some important but periphery characters and focus on the cat and mouse hunt by protagonist Mike Delaney (The Monk) for the antagonist Lucius Gynt (The Priest). He also felt that the reader was being given too much advance information that meant they enjoyed the ride, because the story is pretty original, without experiencing much suspense.
I wasn't sure if he was entirely right because I drip-fed information throughout the book rather than dumping heavy chunks of information on the reader. But not enough, obviously. He said there was a little too much telling and not enough showing. Now I am very aware of this and try to make sure I show action rather than make my presence felt as the author.
So I rewrote a good fifty percent of the book and, you know what? He was partly right. I put new scenes in, explored new avenues and pretty much tightened up the thriller. 
Still not enough, says the agent. Still too much telling not showing. Where, I said? He even pointed out a scene early on where Mike Delaney brings his colleague Bob Messenger up to speed on the recent murder of his wife; filling in the gaps and explaining what's been happening. I do actually drip feed that material elsewhere in the book, here and there through the eyes of her killer.
Now, realistically, you cannot show absolutely everything. In order to show that information, I would have to have gone into flashback, write his wife's murder in gory detail and increase the word count. And if I did that each time a character explained something the book would have been as big as the Bible.
I have read countless crime thrillers (particularly true in the case of police procedurals) where masses of information is explained, discussed, argued about etc. If you had to show every aspect of a police investigation the book would be a million words long.
But, I do intend to make some changes. I might archive the book, withdraw it from publication temporarily, work on it, focus on other books to market and write a new book.