Standing armies aren't useless but their public reputation has far outstripped their utility.
Having a standing army of 3 million is not effective if some kids with a laptop can bring down your entire power network.
We will always need a standing army for a variety of reasons but if we're going to spend money then I'd rather it be kept for weapons that are more cost effective. When you think about how much it costs to train, feed, pay, outfit, equip and support 1 solider in their service history then they're fairly expensive. Not aircraft carrier expensive but not cheap either.
Conscripted armies outside of total war situations, which will never happen in a nuclear equipped country, are always a really bad idea and arguably steeping into authoritarianism.