Since we've been eating oxalic acid for millions of years I highly doubt it's a problem for us. In fact it acts as an antioxidant, can inhibit the growth of many bacteria/fungi, and can bind to heavy metals like lead and mercury.

It makes sense to avoid stuff high in oxalic acid if you're at risk of kidney stones but it seems silly to worry about something we've been consuming for longer than we've been a species for

I have no opinion on whether it is a problem for people in general, but my observations after switching to a low-oxalate diet, then introducing high-oxalate meals as a test are that it is definitely a problem for me.