I don't disagree that the season was a failure as we were aiming to finish in a European position and didn't. In the end though, the league table shows we missed out by quite a narrow margin, in relative terms. When you consider how close we were to e.g. Leicester in the end, the holes in our squad may have been overestimated by our critics and the job done by our manager underestimated.
I think the goal difference suggests we were lacking quality - but we would be, we were ravaged by injuries and nowhere near a finished article Ancelotti side. I think it shows Ancelotti had to fall back on his own nous to win games when the XI simply weren't good enough and that he was successful I.e. the squad overperformed at times.
I definitely think people, not necessarily you, have been too quick to dismiss a 10 point gain on the basis that it only got us 10th position. It got us much closer to the teams above us and much further away from the teams below us. Thankfully it doesn't tell the full story.