Amazing how far Miami has fallen in three years.
That can be said of just about any team that has been on a run of success/titles. The 80's Lakers and Celtics didn't accomplish much of anything in the 90's after Magic/Worthy/Kareem and Parrish/Bird/McHale left. The Bulls haven't won anything since they broke up the teams that won 6 titles. The Lakers and Celtics haven't done anything since they won their last titles in the late 00's, etc. In a few years, it's likely the same will be said of Cleveland and GSW. The outliers, of course, are the Spurs who have managed to remain championship caliber for about 20 years now.
You seem content with mediocrity.
It's not about being content with mediocrity, it's about understanding where your team is and what they have. As bks said, you don't try to fool yourself into thinking your team is better than they actually are.
I won't attend games to watch a team that hasn't a chance at the playoffs.
And that's your prerogative. However, when a team is going through a rebuild, fans need to be patient and adjust their definition of success.
As a Lakers fan, I am enjoying watching the kids learn the game and grow, even though it often means watching them lose. Now, in 2-3 years, if I'm still watching them learn the game and grow, when they should be playoff caliber, then I'll become more impatient with them.