Unfortunately, there is no way to set a Season Goal. If you are in a simulation league that really will not affect you very much so you are not missing out. If you are good at playing Madden and plan to do a user play league then that would be the only reason to really want access to it. The XP alone is just not enough for the risk of being fired.
Many people get too greedy and end up losing their team of 2k plus XP which doesn’t really make sense if you think about it. Gambling all of your hard work for such a small amount of XP. However, It would be nice if they implemented Season Goals for Owner mode in the future.