Josh Zirkzee and Marcus Rashford both scored twice for United on the day.
Dyche said afterwards: "Early in the season there was too many mistakes and that was the same today. In the first 32 minutes I thought we looked a good outfit, we looked progressive. We played well and opened them up.
"One mistake led to another mistake and before you know it you're 2-0 down and then a third one straight after kick-off and that is my biggest gripe. It goes to show if you don't stay tuned in all the time it doesn't work for you and that was the case today.
"We've eradicated some mistakes from the start of the season. It is very difficult when you make such glaring individual mistakes. It is a very difficult task.
"This has to get parked quickly. I don't expect our team to make so many mistakes again. They are well versed in this scenario, it has been here for three or four years at this club. We are trying to break this pattern of work for a breakthrough, drop down, breakthrough, drop down. That is the next challenge by reacting in the next game. Every game is a big game, it is true for Everton."