I'm a FE developer (Mainly React/Node/React Native Development) and I'm still using a 2012 13" Macbook air (8Gb) as my daily driver at home. There's a noticable difference between it and my work (granted still relatively old) 2017 MBP 17". Running builds and an entire test suite maybe take twice as long but it's overall very usable and I see no reason yet to upgrade.