With Inter Milan defender Alessandro Bastoni sent off before halftime, Italy and Bosnia played out a 1-1 draw through to extra-time before the hosts won the shootout 4-1 on Tuesday night.
Spinazzola said at the final whistle: "It's a nightmare, it's true. I've been with the national team for nine years and I still haven't played in a World Cup. It's bad for everyone, including us, for the group we were.
"Even today, with 10... We could have done much better, it's a huge disappointment."
He also said: "Football is a series of episodes. We had three chances to score, but now there's no point in talking. It's a huge disappointment. I hate to see the boys crying. I hope the curse ends now and they can play in another World Cup."
On coach Rino Gattuso, Spinazzola concluded: "The manager was an incredible surprise. I saw everything a coach needs, and I don't think he needs to be changed."