The result means that Arsene Wenger will not end his final season as manager of the Gunners with a trophy and would have not won a European competition during his 22-year reign in charge of the club.
"I can understand the frustration with Ozil," Seaman told talkSPORT.
"When he's on song, he is fantastic, but there have been quite a few times in big games when he just hasn't turned up and last night was one of them.
"Sometimes he looks like he's not bothered or he's getting upset and he's not happy with other players, but I think that's just the way he plays.
"It's so frustrating because he's got so much talent and he is such a good player, but he needs to turn up more often. I can totally understand why the fans are so frustrated."
When speaking about Bellerin, the former goalkeeper added: "Over the two ties it was down to two basic defending mistakes.
"Once Atletico went 1-0 up it was game-over. "We all know they can defend a lead, they remind me so much of the old Arsenal.
"I think Bellerin is a better attacker than he is a defender, and for a right-back it should be totally the other way around.
"He's got the pace but, for me, there's just an art to defending and it looks like he's lost it a little bit."