The last episode of Secret Invasion sucked so bad that it was sponsored by Hoover. The last episode was enough to make the rest of the series sucked. It was more egregious than the last 2 seasons of GOT.
I don't disagree with the last episode being terrible, but it doesn't ruin the whole series for me, in the same way, the last 2 seasons of GOT doesn't ruin the first 6 seasons for me.
I really liked and enjoyed SI until that last episode, so I'm not gonna say the series was terrible based on one episode, even if it was the last one.