Celtic lost 2-1 at home to Ajax on Thursday, ensuring they will finish bottom of Group A.
"We haven't been good enough in the small details," Deila said.
"We're going to be ready next year. That's the message to all the fans, and that's the task that I have and everybody in this club has."
Celtic, who face Fenerbahce in Turkey for their final group game on 10 December, have won only eight of their 25 European games under Deila.
"There are a lot of players that haven't played so much at this level," he said. "I see a lot of talent that will develop and learn from these games.
"You see [Callum] McGregor coming forward. You see [Kieran] Tierney. You see that [Jozo] Simunovic can be a really good central defender. [Stuart] Armstrong is getting better. You see a lot of things.
"I think a lot of people see the whole picture. I think they see a lot of progress."
Asked whether Celtic will look to alter their strategy in the transfer market, targeting more established players, Deila replied: "We buy talent, players who can be Champions League players.
"There's nobody that comes in and just gets to be a Champions League player in the first game. You have to develop them through time.
"It's very, very hard to bring in a player that has played a lot of Champions League football; that's a different level, of course.
"But we have created a lot of Champions League players and we're going to do that in the future."
Deila confirmed Charlie Mulgrew, who left the field after Ajax's late winner, reducing Celtic to 10 men, had pulled a muscle and "could not run".
He also insisted the season is "not over" for Celtic, who are top of the Scottish Premiership.
"It's not like we're going to close down everything until August," he said.
"We are leading the league by six points, we are in every tournament, so I think it is very wrong to put it like that, that the season is over.
"We are very disappointed. I am very disappointed that we are not through, but that's done now. Now, we can only look forward, and that's what I'm doing."
Manager Ronny Deila said Celtic will be "ready" to compete in the Champions League next season despite their exit at the Europa League group stages.