Okay first off.
The Oilers went from a team that missed the playoffs for a very long time to a team that made it to round 2 game 7 last year.
Second: During that long time looking from the outside (2008 draft to 2016 draft) they drafted exactly 4 players outside the first round that have played at least 100 NHL games (
Rieder,
Davidson, Lander and
Marincin).
Not surprisingly they have had problems with good depth for many years.
Peter Chiarelli was brought onto a team that was to put it nicely an absolute mess with many of the players on that team having developed losing habits and (no doubt) a team culture that was only going to cause them to lose even more. He has made several mistakes during his term as GM with some of them being big ones (Griffin Reinhart trade, Hall trade, etc) and he signed some players to deals that are or will hurt the club longer term (Lucic deal, and so on). However, he at least has shown that he understands the team's real weaknesses and hasn't been afraid to try and make a move to address those weaknesses.
I wouldn't fire the GM or the Coach. This situation Edmonton is in is a situation that does NOT have an easy fix. It will take years for the Oilers to build up their depth even more and to continue to make moves to change the group's culture to one where the players commit themselves to a 60 minute full game with a complete work ethic in each game.