We all agree Avila was a bad trader. To me it came down to being too greedy. I know that sounds ironic since he seldom did get a good return, but it's not at the point of the trade where his 'greed' did him in, it was in trying to both use and trade the same resource, which just doesn't work. Fulmer being the easy example. He didn't want to sign Fulmer, but he held him this year hoping the team would be good enough that Fulmer would be a difference maker and so it would be worth it to drain his trade value. But of course it blew up in his face. The team didn't "need" Fulmer for it to accomplish anything as the team accomplished exactly nothing, meanwhile Fulmer's trade value ran out as he became a rental and we got nothing, nor did the Tigers ever pursue him lock up as a longer term resource. You have to commit one way or the other. You are either selling out to win or you are building for the future. Either might work, half and half is fatal.
Al's problem is the he was always half in and half out. He always talked the long term game, and maybe organizationally that were/are committed to a long term view and build process, but in the immediacy of trading, he pretty consistently sacrificed the preservation of long term roster value for short term gain that mostly ended up unrealized anyway.
Couple that with the team's inability to successfully identify good prospects in other orgs when they traded 'down', and here we are.