Gakpo, 23, moved to Liverpool from PSV Eindhoven last month but in six starts he has yet to score.
Liverpool have failed to win in the league since the turn of the year, and were most recently thrashed 3-0 by Wolves. Koeman said their bad run of form does not benefit Gakpo's game.
"You can see that, that he has ended up in a team that is not doing well," Koeman added. "Then it becomes more difficult for him, as a new signing. You are tested right away. And if you don't score or you're not important and you don't win any matches, it's very difficult, especially for a young player. If that's was someone aged 28 with experience, it would be different."
Koeman said it was good to have young Dutch players moving to bigger leagues but it could also be difficult for them.
"The level in England is higher than in the Netherlands, but they are also young boys, aren't they? Like [Ryan] Gravenberch going to Bayern [Munich] and not playing. Then that is difficult," he said on a YouTube show hosted by former footballer Andy van der Meyde.
The new Netherlands coach, who began his second stint in charge on Jan. 1, said he was keeping a keen eye on all Dutch exports as he considers his first selection for March's kick off of the Euro 2024 qualifiers.
Koeman's side take on France and Gibraltar in March.