It was hard luck for the visitors, known for their attacking tempo this season with 66 tries - the highest of any team - after they outscored their opponents by two scores to one.
But admitting experience had just won out on the day, Townsend refused to be too downbeat about his young guns after seeing encouraging signs of improvement.
"The better team is the one that scores more points," Townsend told the Scotsman.
"Leinster just had a bit more experience, they were smart around the breakdown and they got penalties there.
"They just had the edge over us there. Credit to the Glasgow players who played at a real tempo. They were cleaning rucks quickly, supporting the ball and a game like that really tests your fitness.
"The team have all improved from last year. They enjoy their rugby.
"They like playing at tempo, you can see the passing skills, the evasion but we're in the same position we were last year and we know we have to be better to get into a final."
"It's probably where we are. I think we need some more patience in there.
"Our last try was exactly what we need to do in the opposition 22. We need to balance the risk between offloading and keeping the ball, we know we have to learn and get more discipline in that area."
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