I definitely left it too late. I was in a privileged position where my parents were able to help me a lot during my school/university years, meaning that I never had to worry much about money. When I started working and my parents stopped helping me financially, it took me a few years to realise that I was spending more money than I needed to every month, sometimes even more than I was earning.
Monzo definitely played a huge part in helping me shift my perception of money and how I was spending it – ultimately putting me in a position to finally start saving.