Everton matched United in most departments but defeat strengthened the sense of under-achievement that has enveloped their Premier League campaign.
The Merseysiders remain 12th in the table and, despite reaching the semi finals of the FA Cup, were booed off by their own fans at the final whistle.
Manager Martinez said: “We all are (booing). I think you could hear our boos in the dressing room. It is exactly the same.
“We are a club that there has been a bit of a change of generation. A lot of players have come in but incredible young talent needs know-how and lessons and to develop.
“The frustration we all have is we can see the quality we have in our squad and we can’t really gain some sort of momentum.
“But 1984 is the last time we got into the semi-finals of the two domestic cups and this generation can make us very successful.”
Martinez was disappointed his side could not build on a positive start to the game.
The Spaniard said: “We adapted to the game really well and maybe we shocked Man Utd a little bit. They never seemed to feel comfortable.
“The first half was probably exactly what we were looking for. You look at the little amount Joel Robles was involved for – that is the first time I have seen such a controlling 45 minutes.
“But we didn’t use opportunities of great one-on-ones well enough. In the second half we got into a comfortable mood but we switched off in one action which is an unfortunate, easy goal to concede.
“That moment was a massive blow. You don’t expect to concede when you are well in the game.”