What golden opportunity?
The market is at an absolute standstill. The majority, if not all of the team's flexibility is earmarked for their RFAs. So the majority of the futures that you wish to frivolously spend would be used to free up cap space by jettisoning healthy roster players. In a market where 60 point players are getting traded for no return.
Your perspective doesn't take into account the realities of the various markets. What Tampa did seven or eight years ago is in no way comparable to Edmonton's situation today. Moving money is incredibly difficult. And when that money is attached to a healthy player, there's very little guarantee that you're going to be able to find a tangible upgrade through either market. Not even taking into account how that player would fit into your future payroll.
The reason why the deadline is preferable is because the Oilers, now out of LTI, have the ability to accrue cap space as the season progresses. Spending it all before the season starts eliminates that option and essentially locks in the team's playoff roster day one of the regular season. No teams ever do that.