The Welsh were unable to gain promotion to the top tier of the UEFA Nations League. But Allen has thrown his support behind Giggs.
"It's been a great experience for everyone since he's come in," Allen said of Giggs to Sky Sports.
"A lot of new ideas have come into the camp and many players have had the chance to get game time and try and impress.
"We've spoken a lot about the youngsters that have come into the set up, and that's what has given us a lot of confidence about the future.
"We can't wait for the [Euro] qualifiers in March, it's a few months away and this was our last chance to be together before then.
"Our task now as players is to make sure we're ready to fire when those games come around. We're excited to see who we'll be up against."