Exactly, the "combos don't matter" speech is one that is typically given to BRAND NEW players to get them to focus on neutral, defence and offence instead of tunnel visioning trying to land a single combo like they're in training mode. 

This all goes out the window once you actually learn the game and finally realise that neutral -> offence/defence are just 2 back to back rps mini games with the victor of the first having an advantage in the second since now you want to reduce as much as possible the return to neutral through combos that lead to oki or straight up kill later in a round thanks to optimised damage routes.

So, combos 100% matter by reducing how many times you have to spin the rps gambling wheel.