Lampard defended his decision to make eleven changes as the Toffees' hopes of moving a step closer to winning their first trophy since 1995 were dashed with a 4-1 third round defeat in Dorset.
Manager Lampard said: "We were poor. I made a lot of changes, but the reality of my job is that we want to win every game we play.
"When you go through a season and are not getting many minutes, some players are not happy and want to knock on your door, others want to train well and wait for a chance.
"You have to make the most of your opportunities when you get a chance.
"We treated the game with absolute respect and there was a lot of experience in that side but I learned a lot from the performance, particularly with the manner of the goals we conceded.
"I have to protect players who are playing regularly and we had quite a few players out with knocks. We are going to have a really busy schedule after the World Cup break.
"When players train and ask you to put them in the team and they are paid well by Everton, well come in then and show us what you can do. That was the story of tonight.
"You can only train and repeat but you cannot recreate actual moments that happen in a game, at both ends of the pitch.
"If you make those mistakes repetitively then the answer is simple and that is probably why you don't play so much."
Everton fell behind after only seven minutes when Jamal Lowe opened the scoring with a shot that took a massive deflection off James Garner.
Tom Davies and Anthony Gordon both wasted presentable chances to equalise before Junior Stanislas' close-range shot at the far post made it 2-0 two minutes into the second half.
Demarai Gray\s 67th minute curler into the top corner halved the deficit but Emiliano Marcondes restored Bournemouth's two-goal cushion 12 minutes from time, firing home after Lowe's initial effort had been parried into his path by goalkeeper Asmir Begovic.
It was game over four minutes later when Jaidon Anthony side-footed into the bottom corner after substitute Siriki Dembele had caught Nathan Patterson dallying on the ball.
The two teams will meet again in the Premier League on Saturday.
Asked if that will be his last game in charge, Cherries interim manager Gary O'Neil said: "I treat every game like it might be my last, that is the nature of the interim role.
"It has always been about taking the next game and I am very happy with that. I appreciate that I have had a decent chunk of games to get my teeth into.
"I am delighted with the boys tonight. They put in a hell of a performance against a very good side and we looked like a team."