How important is fitness/physical strength?

Hello,
I think my technique is quite alright, I've got a lot to improve on but it's good.
I overtake people sometimes, but I'm mostly overtaken myself.

I don't live very actively, I walk the dog every day for 20 minutes and do 2x65 min skating a week, that's it (I'm not proud of it either). The most laps I can do before I need to stop is three, but I think I can push it to four if really needed. Other kids can do 6, and are a faster than me too. I'm 16 for reference. So I started wondering if physical strength matters along with technique. Thanks!