The midfielder attempted a penalty kick, but Yassine Bounou saved it, and the 2010 World Cup champions failed all three times.
"It's a shame. Penalties were decided in the cruellest possible manner, according to Busquets.
"It was pretty tricky for us. We tried to exhaust, mistreat them, and locate openings. For the decisive ball, we lacked that tiny bit of luck.
Spain lost to Italy on penalties in the Euro 2020 semifinals.
When asked if he intended to continue playing for Spain's national team, Busquets, 34, was evasive.
The Barcelona player asserted that the national team was now more important than himself.
"It's been a difficult night, but we need to get up and utilise it as practice for tomorrow. Some very young players will benefit greatly from this.
Unai Simon, who had saved all three of Spain's shots in a penalty shootout against Switzerland in the quarterfinals of Euro 2020, was only able to stop one of Morocco's attempts this time.
Simon stopped Badr Benoun's penalty and said, "I think we were better than our opponents for the 120 minutes of the game, but what I say now doesn't matter if we can't find the net.
They excelled in the shootout, which advanced them to the quarterfinals.
Throughout the World Cup, we can see that there are surprises. We could not defeat them, and we did not anticipate being eliminated by Morocco, but this is the situation, and we must now return home.